Hi,@Zikwit 
Thank you for posting your query on our commercial forum.

We would like to share the following recommendations for your reference:

• Optimize client distribution on the 2.4GHz band. You may consider offloading the 33 clients currently associated with the office AP to other available APs or other frequency bands. We generally recommend keeping the number of clients per 2.4GHz AP under 30.
• Please consider creating a separate Test SSID exclusively for non-IoT devices such as mobile phones, and configure this SSID to operate on the 5GHz band, so that only mobile phones, computers and similar non-IoT devices connect to this SSID. Please test if your phone or PC can work properly when connecting to the test SSID.we recommend disabling 802.11rand Fast Roaming for testing.
• We also suggest checking for potential IP conflicts among clients, verifying your DHCP lease settings, and adjusting the lease duration to 24 hours for testing.

If possible, we would greatly appreciate it if you could conduct the following tests and provide the relevant information to us:

• When the issue of "WiFi shows connected but no Internet access" occurs, please run a ping test to 8.8.8.8 and let us know whether the test succeeds.
• Does the disconnection issue occur on all devices, or is it mainly concentrated on certain specific types of devices? How frequently does this issue occur?
• Have you tested the three APs individually to confirm whether the issue is tied to a specific AP or occurs on all three units?

Update:  i tried to bump 5ghz to 80 mhz instead of 40mhz and I've started to have more intreruption on my latop but the catch is that the Wifi connections is still stable since I can ping my home assistant no problem locally but 0 response on ping 8.8.8.8. FOR CONTEXT all my 5ghz radios on the aps are set to low so that they are not interfering with each other 

  @Jeremy_12 I am going to try the test SSID Separately for now ( only on 5Ghz )  

Regarding the better distribution of the WiFi Clients this is the best that I can do since I have a lot of Shelly relays that are on the WiFi network ( but keep in mind that I had the issues even with far less 2.4 Ghz clients connected as well  ). 

Also the GHub main SSID was designated as only 5ghz and 6 ghz once but I had a stubborn single IoT devices which didn't t want to change WiFi settings at all so as temporary fix I had 2.4 on that enabled as well. 

I've also changed from 120 min to 1440 min for the DHCP Lease on all vlans . For the IoT devices I've actually did DHCP reservation for all them.

Regarding if I can isolate the issues to one of the APs, I had the issues on both EAP772 since these are the ones that I actually use ( 1 on the ground floor and 1 on the first floor near the bedroom and having issues with both ). 

The devices I ve encounter interruptions are all ios device, 2 mobile phones and 2 laptops, I don t have other ones  on which I can really test that out.

I will try to do the ping 8.8.8.8 if i get the chance on my phone or my laptop while having a short interruption.

Is there any other settings to switch off or on in the meantime ?