First thing I'd try would be to swap places for the problem Roku with one of the other ones to see if the problem stayed with the location, or stayed with the particular unit.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X