We've never been able to replicate the issue in uCenter so we've not been able to log it as an issue with Ublox directly. However a number of people have replicated the issue using different code and microcontrollers. I suspect Ucenter may be automatically reverting to max performance mode (I need to get a logic analyser on the case and check this).
The biggest give away is the time stops incrementing. Once the module is locked it stops responding to any commands on the serial port and has to be reset. Oddly it seems to take a little while to get into this state and you can fix the issue simply by putting it back in max performance mode. This issue definitely occurs when using UBX to poll for positions and may occur when using NMEA.
I'm not sure for most applications the low power mode needs to be used at all on the newer ublox modules. The values for the MAX-7Q are 22mA (6Q 50mA) under acquire, tracking (i.e locked and in max performance) current at is 17mA (39mA 6Q) and power saving reduces this to 5mA or less (15mA on the 6Q). We've observed the issue on the 6 and 7 series.
I'd be very interested if anyone can replicate this using gpsd. As a side, and probably related note, you can hang/reset a 6 series on demand by putting it in 10 second cyclic mode before getting a lock .
Regards,
Anthony