Basically the Roku stick is a piece of crap and I would NEVER but it again. I literally fixed my it from freezing by tearing it out of the back of the TV and throwing in the regierator for 10 mintues....all in the middle of GOT - you can imagine my frustration.
Or you could buy an HDMI extender for it and see if that helps. It could be that the TV is generating heat too, and the Roku is overheating because of it. Also, have you tried plugging the Roku in with an AC adapter? Maybe your already doing this, but some TV's USB ports don't supply enough power to consistently run a Roku stick.
Yeah, I got some Rokus. https://youtu.be/d1CSEeqWl10