I've tried plenty of boxes over the years and the most stable box sub £80 I've ever used is the Amazon fire TV.
Mainly because of the decent remote, doesn't constantly crash. That's not to say all android boxes are terrible but there are far too many cheap generic android boxes which just get rebranded.
If you don't want the fire TV whatever you look at make sure it's at least android 7, 2gb bare minimum and has a decent remote