idk if garmin has a similar sensor pairing process to wahoo, but with wahoo, you have to "add" any new sensor before it recognizes it. If garmin does not use a process in similar fashion & has an auto detect pairing setup, then it makes sense that it is "corrupting" files after a group ride while nearby other like sensors.

I would pull the batteries from all the sensors & do a factory reset on the device. Once it is booted up, install the batteries back in the sensors & attempt to pair all the sensors again.