@Hank21 this ticket was unexpectly closed without resolution. Does TP Link have a solution to the firmware upgrade issue?

  @Hank21 

Do we have any update on our issues ?, what should be the procedure?

I've had similar issues after updating firmware.  I have 4 devices in close proximity to the EAP615.  After about a day just one or none would be connected, one wouldn't connect to any AP and the rest would only re-connect to other APs (not 615) in range.  After a reboot it would work again for while.  I tried disabling AP locks, RSI Thresholds and other features, but that did not help.  The EAP615 is the yellow line in the graph of AP Connected Clients below.  I updated the firmware soon after it was released and I just "downgraded" today.

  @D-C 

I had similar issues with mine. I also experienced bad connectivity with a device that is wired to the AP, suggesting it's not a problem with the WiFi. In my testing, I noticed that the issue seemed to be not between the devices and the APs, but between the APs and the switch. If I measured ping times between devices directly connected to the switch and the AP itself, I would see high latency variation and packet loss that would steadily get worse the longer it had been since the AP had been rebooted. Similar tests between other devices connected to the switch and another different model AP didn't replicate the results, suggesting the issue is the two APs of that model (615-wall). I conducted these tests simply by running the ping command against my various devices and seeing what the latency and packet loss was. Downgrading the two 615-wall APs to the previous firmware fixed the problem.

A few comments:

1. I notice that an update of the previous v1.1.x line (to 1.1.7) has now appeared on the TP-Link website, dated 1st March. Is this a tacit admission that there are issues with 1.2.3? There is nothing in the Release Notes to that effect. Obviously 1.2.3 introduced a large number of changes but from the version number they must have had at least three previous attempts at a clean version before they finally released 1.2.3.

2. I run my APs in standalone mode for the moment (may eventually add the OC200 that I have waiting until I have the time to get my head around it). One problem I have with this product is that whatever I do I cannot get it to log in to my mail server to send log updates - I get two error messages, either "wrong mail address" (it is not wrong!), or "Fail to Connect the mail server" (the settings are definitely correct - I have checked, double-checked and triple-checked them). Maybe not a big deal but annoying. My mail server is on my local network and I have tried disabling authentication for LAN connections on the server, and used the IP address directly to minimise the failure modes, but even having done this it just does not work. The error messages are way too vague to be helpful.

3. One of the other issues I have is that the signal strength of some devices connected to one of the three WiFi networks suddenly drop after a while and although they are still connected there is no data flow. I have to dis- and re-connect to the SSID when the signal goes back to full strength. This problem is with iPhones and iPads (not tested with Android), and one of the ways it manifests itself with iPhones when using WiFi calling is that the call audio drops for a few seconds but the call remains connected. It always comes back again but one has lost a few seconds of the conversation. It seems to happen about every five to ten minutes or so. I have now tried fixing the channels of all WAPs to rule that out as the cause - I speculate that possibly the WAP is changing its channel and the device is not following, or another further-away WAP is intruding on the channel and taking over the connection, but I have no evidence at all to support this.

I upgraded to the official controller firmware (2.13.2 Build 20240110 Rel.78759) and then upgraded the EAP615 to v 1.2.3.  It's been a week now and the AP has not been disconnecting the clients as it was before.