Found out (Locosys confirmed) FW version < 1.4 have more problems with not erased datalogger memory.If it's full datalogger memory don't delete old trackpoints to make space for new and device "freezed"  I clear now starting before each session the datalogger,seems working a bit.

Wondering why Garmin GPS devices have never freezes and GT-31 sometimes. Since release Gt-31 seems there is still freezes possible with all version.