Ortovox has discovered that batteries that are at the small end of the standard size can be dislodged in the M1 and M2 avalanche beepers if they're bashed hard enough. They will provide replacement battery covers free of charge - see the ortovox website.

Apparently some other brands have the same problem - so if you have a beeper, check with the manufacturer.

Yes, I have already ordered new battery covers for the club's beepers.