Hi,
I open previously a Zendesk ticket #118094 for this issue, and also describe it in this topic.
I also lost twice my logbook and my progression.
But, not totally: I flew three bush trips, and was awarded of a success. In my xbox live account, all is fine, not erased. In FS2020, the progression show 100%, but the total say (for bush trips) : 0/10
To overide that, I reflew the las leg of each bush trip, and miracle , the counter now say 3/10 as expected. But of course, I’m far to the 50 hours of flight because this one is based on the logbook.
This bug make quite unplayable the Xbox version, as we are unsure if the logbook will no be lost one more time, soon or later 
I also notice that the logbook record wrong things, especially when flying the bush trips. I have the Alaska bush trip in progress, and sometimes, it record nosense datas. Very weird!
When I finish a leg, the screen display the correct result (departure/arrival/fligh time as expected) - but , if i return to the main menu and take a look at the logbook, I see 00:00:00 as flighttime, and arrival airport is replaced by the departure.
There is defintely something very buggy in the logbook.
For the learning flights, I also get a counter of 0… but if I reflew the same lesson, and even get a “C”, it is recorded again as a “A” and counted.
Edit: don’t forget to VOTE for bugs (at the top of the page/topic) if you wan’t a chance to them solved.