I put off publishing this information because I couldn't find the source that originally suggested this solution. It might have been this page in Russian where I originally saw it 🤷. Honestly I didn't expect it to work.

Problem

Out of four separate Onn 4k Google TV boxes one would experience frequent remote control disconnects. The remote would flash a red light when any buttons were used. Most suggestions online recommended checking the batteries and cooling the TV box. Neither fixed the issue.

Solution

Summary

What ended up actually working was to heat the internal bluetooth module, an ASKEY 8822CS, with a hot air rework station. If you don't already have some kind of heat-gun then this may be overkill for a $20 box, but I already had a cheap model from Al that was only around $25.

Where to heat

8822CS chip on circuit board

I'm not entirely sure if the issue was with the edge soldering of the chip itself, or one of the components on it. While heating it I removed the silver cover and just generally heated it all until the solder of the unpopulated USB port just below it felt a bit soft when poked with a wire. If you try it I'd suggest just heating the edges first and see if that works.

Since then I've had zero issues with this particular box.