I have two Samsung devices. One is a Galaxy Tab S2 running Android 7 and the other is a Galaxy Note 9 running Android 10.
In both cases I keep getting devices disconnected when I tried to connect to my Plusnet route or after a period of using the route. It can also occur as I go further away from the router. For example upstairs into my bathroom. I have a fibre optic connection.
The router is in my dinning room downstairs, which is below my upstairs bedroom and the bathroom if off my my stairs bedroom.
This isn't a long standing issue and only seems to have started in recent months or weeks. It is worse for my Tab S2, which runs Android 7, than my Note 9, which runs Android 10. The error messages on Android 7 Tab S2 is "authentication error occurred". On Android 10 Note 9 it is: "Couldn't authenticate connection",
It can sometimes take quite a few attempts for my Tab S2 to connect. I think there is also an issue at times with my Chromecast, which is located in my sitting room, also losing the WiFi connection. All of them are on 2.4GHz band when I just checked. Restarting the route can at times solve the problem but within a day it returns.
When my Note 9 fails to authenticate it then switches to use the mobile data and if I don't notice I suddenly find large amounts of data being used, after I get a notification reporting this. It doesn't try again to authenticate when it can't, even though if I try to connect, it does, abet not always. Given we are in lock down, I have now switched off my mobile data.