My flights are erratically logged. Some are logged correctly, usually if I turn off engines in a designated parking spot and switch off avionics. But I have noticed some flights have a much shorter recorded duration than the actual flight. Often it seems to be that if I start a flight with no designated destination, then select an airport and land there, it is timed only from when requesting permission to land from ATC.
If I don’t shut down and ‘complete’ a flight, I most often do not have the flight recorded in the log.