More explanation may be necessary for users to understand the problem.
The file in reference is sync’d with your Microsoft Xbox Cloud account and is limited to 16MB.
It’s path is: C:\Users\username\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\SystemAppData\wgs\Random Number\Random Number
The file size can reach only 16MB.
The file stores the Pilot profile with Activities, Achievements, Logbook.
Why is it important? Your Logbook is the main limitation. I currently have just over 2500 entries. I hit this limitation in July 2022.
Interestingly, 741 of of my entries are zero time entries where I entered a take-off position and either changed my mind, was testing a Mod or Livery or Asobo made an additional entry during exit if flight).
Each new flight since then is displayed in the logbook but is not synced with Xbox Cloud. When exiting the sim, those new entries are expunged.