I had this error on 02/21/2021 for the first time. Back then I reported it to Zendesk and nothing really happened to this day. At that time, EDIT: 184 hours were lost in my logbook. I’m sorry it’s affecting so many all of a sudden. If the developers had taken care of it back then, they could have saved us a lot of trouble. So far it has happened to me three more times, and each time the logbook was empty.
It’s time someone took care of it!
In my opinion it has something to do with how often the XBox license is checked. If the connection to the server is lost in between, then XBox throws me out and when I log in again, Xbox syncs my account again. But since nothing is saved locally, all flights in the logbook are overwritten, i.e. deleted, with the locally saved data.