Hello, I have the same issue with many FM2200 Devices that are not able to synchronize clock.
Terminal shows something like this:
-[2018.1.9 10:32:49]-[NMEA.FILTER]->WARNING! Bad GPS Timestamp: 1515493974
-[2018.1.9 10:32:50]-[NMEA.FILTER]->WARNING! Bad GPS Timestamp: 1515493975
This started happening after 1 Jan 2018 but not exactly in the same time, some devices on 1 Jan, some on 2 Jan, some on 3 ... so on . So it is also related to some kind of counter that ins in the firmware.
It cannot be only date/time related, which really makes me thinking is is not a simple bug. Someone should investigate Teltonika for this "bugs".