Same thing is happening to me (2018 Tahoe Premier). While at home, I noticed that my phone would gain/lose a connection periodically. But it happened so quick I didn't know what it was - the car "waking up" could be the culprit. Temps have been below 30F and my battery died. It died again after a recharge and I figured it was time to replace it since it's been 6+ years. New battery died after the first day, but it's possible that it wasn't fully charged to begin with? (Although that seems unlikely). I have not changed the location of the key fob when it's been inside, but will try to keep it further away from the vehicle. I may also try to check under the fuse box, but I can't see how moisture/ice would get there. While it has been cold, there hasn't been any recent precipitation. Keeping a jump pack in my car for now...