Make a back up your MSFS. Simply copy the folders in C:\Users<username>\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache\Packages
I found there was a problem when I tried this a few days back. Windows is stating I cannot copy files from there. I got past this by making a rar (compressed) file on another drive.
Once you have a copy of your files, uninstall MSFS totally.
Reinstall it to reset the errors you have currently.
When MSFS started to do the big update close it down. Restore your files back into place.
This should sort out your issue.