Took it out of the case, drilled a bunch of holes in it for air circulation, stuck a small heatsink I had around on the bluetooth chip. Looks ridiculous, but hasn't unpaired since. But weather has cooled around here lately, too.

Set the device on an ice pack. Specifically the side with the sticker. That’s where the Bluetooth module is.

Have u replaced the batteries? That’s what fixed mine.

This happened on mine so frequently that I have to use HDMI CEC to control the box. After a while, the remote became unusable for anything(light solid green). I retired my box in favor for a roku

During setup of new device an update was pushed to the remote. I have not noticed any issues but I alternate between a Google remote and the ONN remote all the time. Which ever is closer, don't have a preference.

Before I read your post, and had only read the title, I put it down to overheating.
A lot of the boxes are suffering from overheating lately, maybe China cutting corners as prices rise, 1 of 100 or 1000 may suffer idk.

Try adding thermal paste and a heatsink or copper shim. You can use a large copper coin instead of a shim.

Adding small holes along the side can also help. Adding holes on the bottom may not really help as much, unfortunately. Adding holes on the top should help, but may look ugly, in which case you could just take the top off altogether.

It sounds like the same issue that was happening to a few other boxes, but one other android TV box in particular. And overheating can also cause other weird issues apart from unpairing - which is noticed more due to the separate chip for the RC.

I would buy a new unit and pair the new remote with the old unit to see if it still happens. l mean, the cost of a new unit has to be less than all the trouble you are about to embark on trying to "fix" the old one. Or am I missing something?

Can you please test it with a Bluetooth speaker or something while you paired it? Will it be unpaired?

It looks like there is a problem with the board of the RTL8822CS module (which is responsible for wifi+bt).

From the moment of installation, the box lived behind the TVs, the TV case heats up to 40C and there were no problems for about six months. Then, an hour and a half after the start of using the box, the remote control began to fall off (the batteries are 100% charged), if I try to pair the remote control again, it constantly switches between prepare and connecting on the pairing screen until the box cools down. The same situation with pairing remote control from another onn box, so the problem is not with the remote.

After the back cover was removed from the case the problem has gone. After few tests I managed to find out that with local heating of the RTL8822CS the problem with remote control appears immediately.

First the attempt was made to attach a small heatsink to RTL8822CS , then the metal shield from RTL8822CS was removed and the heatsink was sticked directly onto the chip - without much improvement. Then there was an attempt to heat the entire board of the RTL8822CS module with a soldering dryer - and the problem was gone even with the case closed. But after about 3 months, the problem returned, and now even with opened case.

Datasheet of RTL8822CS says that the antenna is common for BT and Wifi 2.4GHz, when the remote control is failing, there is no visible problems with wifi 2.4 / 5GHz connection, perhaps because both antennas are used for wifi at the same time.

Probably the reason is that over time, the soldering of components is broken somewhere due to frequent temperature changes. Perhaps boxes that are initially operated at lower temperatures (without additional heating from the TV case) live longer and are less likely to encounter this problem.

What kind of Tv do you have it hooked up to ? Ive never had issues with my Onn box hooked up to my Lg Tv or my Toshiba Tv. My friend has a vizio Tv and he's had issues with his remote like you are having. have you tried a different Tv ?