I have an issue on multiple sites with different configurations and can't get to the bottom of it.

Site 1 has an ER605 connected to a Mikrotik router with a USB modem. The Mikrotik device does the VPN and DNS over that. DNS on the ER605 is set to be the Mikrotik device. Also a single EAP653 connected to the ER605, managed from a software controller on a remote site.

Site 2 has 3x EAP653, an ER605 and an OC200 and is connected to the internet via PPPoE with the ER605 being connected directly to an ONT.

On both sites Android devices constantly disconnect and when they are connected are often painfully slow (speedtest.net results are usually <0.1Mbps). Other WiFi devices seem to be connected without issue.

I did initially have WPA2 AES mode on all SSIDs and things were fine (I think, or at least I didn't notice any issues for a few days). I turned on WPA3 for testing some devices (on both sites) and the WiFi ended up exhibiting various issues so I set everything back to WPA2 mode and the problems persisted. I turned off all the usual things (airtime fairness, band steering etc) and set PMF back to disabled with no difference. I tried tweaking/setting as many things as I could find reference to on other threads and no improvement at all. Eventually set up a new 2.4GHz only SSID on site 1 and connected devices to this and still no improvement. Swithced to 5GHz and it seemed to work sporadically but still not really much of an improvement.

It feels like something that was set when I activated WPA3 caused an issue and some setting somewhere is not being reset on the APs or the APs are not being reprovisioned properly? So currently I have 2 non-working Omada systems. Trying to refrain from just switching back to the Unifi APs they replaced but I will have to if this can't be fixed.