Which model is it? As far as I’m aware all the Unifi APs need the controller for config. It doesn’t need to stay running unless you want a couple features for large deployments but you do need to run it to set things up initially. The Air Max / uisp lines are the ones with web based config.
Do you have a continuously running unifi controller or is it only running when you do the config? Does it do the same thing with the controller opposite to how it is now (ie if you aren’t running it does it do it when you leave the controller on)?
Are you running the 2.4 and 5 as separate SSIDs or the same one?
Are you on the latest controller and firmware?
I believe you can change the scaling algorithm obs uses? Right click the source and go to “scale filter” is what Google is telling me, not at a computer right now. I think it defaults to bicubic which should be ok though? The switch does its own internal scaling a lot of the time and that can look pretty bad though, but unless you get into some serious shenanigans that’s basically baked in.
Ah, ok. The Unifi stuff is a bit weird like that. I recommend installing the controller on a computer if you continue to have issues. You don’t have to run it all the time, just use it for config and then turning it off is fine. It’ll give you way more information and control over exactly how the AP is set up.