Lat/Lon information disappears intermittently

I am using 4.7 location with the gmap modules, and geocoding disabled.

The problem is that the location lat/lon data attached to organic group nodes intermittently disappears. This doesn't happen for all nodes, nor can I find any pattern to the nodes it does affect. The data sticks after it is entered, but disappears after a day or several days, seemingly without any edits of the nodes having taken place.

Any suggestions for further diagnostics or how to solve this problem?

Thanks! David.