FYI, while working with my V2 (coin cell) multi-purpose sensor, and discovering the battery issue (the coin cells positive/outside electrode must extend most of the height of the cell to work properly) I also discovered that there was a firmware update for these beasties.
When I went to “Devices” in the web interface and selected one of these, it showed a “Current Version” of “0x01015310” and a “Target Version” of “0x1F015310”.
After enabling firmware updates at the hub (there are other posts about that) my sensors did indeed update, and the Current version now matches the target version.
I suppose this might help with a number of issues folks have had with these sensors (though not the structure of the battery contact, of course).