It seems there are lots of problems reported on this forum with such devices.
I take it that you have set the country code and tried experimenting with different channel widths?
You could also try latest snapshot to see if that helps.
The RT3200 is WiFi 6 and only £80 on Amazon now. Its WiFi is 100% stable for me (and many other users), it supports 160Mhz width on 5Ghz, has fast processor and lots of ram. Just thought I'd point that out! It was also ultra stress tested with many client devices and it survived that. I will try to find the post on that.