Roman,
The API is setup to only return UBX messages when GPS is locked and outputting NMEA sentences. This is a result of how we package and return this data. For this reason, yes, you would need to see GPS lock before expecting messages.
Is there an event that consistently leads to lost GPS lock? Is it after sending a message? Does your GPS antenna have access to clear sky? I can’t say that I have seen a scenario or heard from a customer that a reboot of the device was required to attain GPS lock. Is it possible one of the messages is configuring the device in an undesirable state?
We only have experience sending the NAV5 message for changing the platform model. That code example is in our SDK (you probably already found it). I have not used the cold boot command. If it forces the GPS to do a cold boot, this will take many minutes or longer to get GPS lock again, I’m assuming you are waiting an appropriate amount of time?
