@Riley_S 

Thanks so much for the reply.  It's taken me a couple of days to find the time to truly work on this but here's the latest.

First of all, the switch in question is a D-Link DGS-1016A -- an unmanaged 16-port gigabit switch.  I've been using it for quite a while (prior to getting the Deco system) without incident, at least as far as I could tell.  I've swapped out cables and confirmed they are not the culprit. Likewise with swapping to different ports on the switch.  

I established IP reservations for the Shield and the TV and, after initially having quite a time getting them to take, both devices are now pulling down their reserved IPs and are connected to the router/internet. Despite this, however, I continue to get disconnect notices from Deco regarding the Shield.  I would note, again, that the Shield itself seems to be functioning quite alright with no noticeable disconnects/loss of access. UPDATE: for the first time since getting the disconnect notices, I tried using the Shield and it had genuinely lost connection/would not function.  

As for the TV, I'm still waiting to see if the disconnect notices persist, as I only sorted out its IP issues about an hour ago.  But so far, so good on it. UPDATE: The TV is still suffering from disconnections as well. 
 

On other thing to mention: you suggested I should give an IP reservation to the switch itself but I don't see the switch showing up as a discrete connected device to my main Deco router, so I'm unclear on how to do that and/or if it's possible. 

UPDATE: I found a post on another forum that described a similar issue.  That poster ultimately concluded that his security camera was the culprit because it was somehow advertising itself as a gateway and was assigning IP addresses that was causing conflicts.  I have an Arlo system connected to this switch.  I'm wondering if that might be the problem, but I'm at a loss as to what to do about it if so.  I'm going to disconnect it from the switch tomorrow and see if the disconnects/reconnects stop. 

Thanks for any additional insight you can provide. 

  @Riley_S 

So yet another update: I disconnected the Arlo Pro base and I have not had a single disconnect in the 12 or so hours since.  I was previously getting multiple notices per hour for each device.  I'm not exactly clear on how it's happening but I'm virtually positive the Arlo is causing some kind of IP conflict.  I'm going to change the LAN IP and have DHCP assign IPs in a different range and then reactivate the Arlo to see if that resolves the problem. 

  @Riley_S 

Well, it apparently wasn't the Arlo and changing the LAN IP/default gateway did not fix the problem -- the disconnect notices have begun again. I'm at a loss. 

  @Riley_S 

Thanks for the reply, Riley.  A lot to unpack here, but let me start by updating you.

I ended up disconnecting both the Shield and the TV from the switch and having them both connect wirelessly.  I also reserved IP addresses for each device on Deco's end.  At subsequent points, I disabled "Mesh Technology" and told both to connect to the main hub (that they were previously wired into via the switch).  They both connected and assumed their correct IPs, but it didn't last.  

The Shield has done well overall. Only a couple of disconnects -- and none in a while that I can tell (I temporarily disabled connection notices because of how many I was getting from the TV).  I still am at a loss as to why it wouldn't play nice with the wired connection, but at least the wireless connection appears stable at this point. (One strange thing to note, however: the Deco randomly changes the way it identifies/names the Shield on my network.  Sometimes it's "Android-8," sometimes it's "Android-5," sometimes it's "Android-3," and sometimes it's simply "Android."  This can cause some confusion when trying to set up connection alerts and confirm that it's grabbing the right IP, etc.  Really strange, as my other Shield (connected via a different Deco hub) consistently shows up as "NVIDIA.")  

The TV, however, is an absolute disaster.  It disconnects and reconnects every few minutes, and will not grab the IP I've reserved for it.  So now I've got a device that routinely disconnects and reconnects from the network every few minutes, whether wired OR wireless.  I know this might lead one to conclude it's an issue with the device itself, but bear in mind that I had *zero* such issues with it on my old Google Wifi network.  I am just at a total loss here, unless it's just that this hub is a lemon of some sort.

To address some of your other questions/points:

- I don't think there's anything else that could be creating a network that the TV is attempting to connect to.  The Arlo was the only thing I could imagine doing this but the problem persisted even after I left it disconnected/powered off for a prolonged period of time.  

- My ISP "gateway" (modem/router) is in bridge mode, so there is no router functionality or wireless SSID being broadcast, etc.  

- I'm going to bypass the switch with my TV and connect it directly to the main Deco router and see if this problem continues.

- Probably shouldn't read too much into the "12 hour" thing as I was just using that more figuratively -- as in the problem came back overnight. It's possible there's something to the IP renewing its lease but I just wanted to clarify my comment with regard to that.  Of course, as noted above, the disconnects/reconnects are occurring repeatedly, every few minutes.  

- I've downloaded the logs that show the frequent disconnects.  I'm going to paste an excerpt below, as it means nothing to me. Note that the MAC address ending in 6b:7a is the TV. That one ending in 9A:BE is a Sonos speaker. Could the Sonos be causing the problem somehow? Thanks again for your help.

Fri Oct 20 18:29:57 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@245]: Group address 224.0.0.251 is Local Network Control Block
Fri Oct 20 18:29:57 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@258]: Group address 239.255.255.250 belongs to IPv4 Local Scope.
Fri Oct 20 18:29:57 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@245]: Group address 224.0.0.251 is Local Network Control Block
Fri Oct 20 18:29:57 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@245]: Group address 224.0.0.250 is Local Network Control Block
Fri Oct 20 18:29:57 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@258]: Group address 239.255.255.251 belongs to IPv4 Local Scope.
Fri Oct 20 18:29:57 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@258]: Group address 239.255.255.250 belongs to IPv4 Local Scope.
Fri Oct 20 18:29:57 2023 user.notice IMPROXY: INFO[imp_input_report_mldv2@471]: MLD_CHANGE_TO_EXCLUDE
Fri Oct 20 18:30:01 2023 daemon.notice nrd[15459]: wlanifLinkEventsCmnGenerateDisassocEvent: Client 00:BF:AF:9A:6B:7A disassociated on APId 255 ChanId 48  ESSId 0  
Fri Oct 20 18:30:01 2023 daemon.notice hostapd: ath1: AP-STA-DISCONNECTED 00:bf:af:9a:6b:7a
Fri Oct 20 18:30:01 2023 daemon.notice hostapd: ath1: ubus call client_mgmt access '{"mac":"00-BF-AF-9A-6B-7A","ifname":"ath1","action":"disassociate"}' &
Fri Oct 20 18:30:01 2023 daemon.notice hostapd: wpa_driver_nl80211_set_key: ifindex=29 (ath1) alg=0 addr=0x55b46e6bf0 key_idx=0 set_tx=1 seq_len=0 key_len=0 key_flag=0x20
Fri Oct 20 18:30:01 2023 daemon.notice hostapd: wpa_driver_nl80211_set_key: ifindex=29 (ath1) alg=0 addr=0x55b46e6bf0 key_idx=0 set_tx=1 seq_len=0 key_len=0 key_flag=0x20
Fri Oct 20 18:30:01 2023 daemon.err hostapd: hostapd_notif_disassoc num_sta 2
Fri Oct 20 18:30:01 2023 daemon.err client_mgmt: wireless client associate or disassociate.
Fri Oct 20 18:30:01 2023 daemon.err client_mgmt: client_mac:00-BF-AF-9A-6B-7A, client_ifname:ath1, client_action:disassociate
Fri Oct 20 18:30:01 2023 daemon.err client_mgmt: client(00-BF-AF-9A-6B-7A) disassociate by if(ath1).
Fri Oct 20 18:30:10 2023 authpriv.notice dropbear[6711]: Pubkey auth succeeded for 'root' with key sha1!! ac:ce:9f:38:a1:34:d2:24:6f:97:ab:11:fc:77:38:5b:62:04:3c:d3 from 192.168.86.199:58690
Fri Oct 20 18:30:10 2023 daemon.err client_mgmt: client(00-BF-AF-9A-6B-7A) disconnected
Fri Oct 20 18:30:11 2023 daemon.err client_mgmt: client(5C-AA-FD-07-9A-BE) not found in arp table disconnect_counter=0
Fri Oct 20 18:30:11 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@258]: Group address 239.255.255.250 belongs to IPv4 Local Scope.
Fri Oct 20 18:30:14 2023 daemon.err udhcpd[15215]: Received DISCOVER
Fri Oct 20 18:30:14 2023 daemon.err udhcpd[15215]: clear ip 1d56a8c0
Fri Oct 20 18:30:14 2023 daemon.err udhcpd[15215]: Sending OFFER of 192.168.86.29
Fri Oct 20 18:30:15 2023 daemon.err udhcpd[15215]: Sending ACK to 192.168.86.29
Fri Oct 20 18:30:15 2023 daemon.err udhcpd[15215]: clear ip 1d56a8c0
Fri Oct 20 18:30:15 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@245]: Group address 224.0.0.251 is Local Network Control Block
Fri Oct 20 18:30:15 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@258]: Group address 239.255.255.250 belongs to IPv4 Local Scope.
Fri Oct 20 18:30:15 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@245]: Group address 224.0.0.251 is Local Network Control Block
Fri Oct 20 18:30:15 2023 user.notice IMPROXY: INFO[imp_input_report_mldv2@471]: MLD_CHANGE_TO_EXCLUDE
Fri Oct 20 18:30:15 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@245]: Group address 224.0.0.250 is Local Network Control Block
Fri Oct 20 18:30:15 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@258]: Group address 239.255.255.251 belongs to IPv4 Local Scope.
Fri Oct 20 18:30:15 2023 user.notice IMPROXY: INFO[imp_verify_multicast_addr@258]: Group address 239.255.255.250 belongs to IPv4 Local Scope.

  @Riley_S 

A few updates to pass along:

- Sonos: I've followed TP Link's recommendation and moved my Sonos speakers from wifi to "SonosNet" by hardwiring one speaker to the main router. I've confirmed that all my Sonos speakers are now using SonosNet.  They do still show up as connected clients on Deco, however.  I understand this is normal/how it's supposed to work.

- I'm still getting some TV disconnects/reconnects but they are not quite as frequent.  However, my Synology -- hard-wired via the switch -- is now the main offending device.  I've had no trouble with it at all before now.  It's now frequently disconnecting/reconnecting, just as the TV was previously.  It has a reserved IP on the Deco end and is successfully receiving that IP assignment.  This seems to confirm the issue is not with the clients themselves.  

- The TV (again, currently connected via wifi) will not accept its assigned IP for some reason.  It's just grabbing the very first IP in the range (i.e., 192.168.86.2).  

- I reconnected the Shield via ethernet just to see how it behaved. It is again getting some disconnects/reconnects, despite correctly pulling its assigned IP.  

- I still need to remove the switch from the equation to see what results.  The problem with this, however, is that I will be limited to hard-wiring two devices, which will not accurately re-create my actual use case.  

I am at a loss, particularly given that the problems are not limited to either ethernet OR wifi -- I'm having issues with both. I am going to both try to connect the devices without the switch and see about tracking down another switch to test.  I have no reason to believe this switch is faulty as I was not having these problems with my previous router, but perhaps it simply doesn't play nice with Deco for some reason?

  @Riley_S 

Another update: I bypassed the switch and connected the Shield directly to the main Deco router.  This is the result.  So it appears clear that the switch is not the culprit either. Again, I'm at an absolute loss unless this is simply a faulty unit. 

  @Riley_S 

Just wondering if I'm going to receive any additional replies and/or help, as it's been a week since I last heard anything.  Do the logs tell you and/or your engineers anything useful? 

By way of update, I recently completely reset my network and used a different hub to serve as the main router.  I used a different LAN IP/gateway.  I even bought a TP-Link switch to replace the D-Link switch I've been using.  

The disconnects have continued unabated, though the Shield has become the main offender (sometimes 6 disconnects/reconnects in an hour) with the Synology disconnecting/reconnecting maybe 6-8 times per day.  The interesting thing I noticed is that the Shield went crazy with disconnects when I gave it an assigned/reserved IP.  It had no trouble accepting the address -- and it's way out of range of my other stuff, and I don't think there's any sort of IP conflict possible -- but it just continually disconnected and reconnected.  Since I disabled to IP reservation this afternoon, I haven't had it disconnect a single time.  

Again, I'm at a loss regarding the instability of my network. There's nothing particularly unique about my setup and at this point I think I've controlled for virtually every imaginable variable.  Very, very frustrating.