There are a few different people reporting problems in this thread, and they may not all have the same cause. I'll talk about a few different things you can try that will hopefully help.
If you have eliminated OneDrive as a factor, other likely causes are a problem with custom content or something getting corrupted with one of the RealFlight files on your system.
The first thing I would do is go to your <Documents>\RealFlight Evolution directory and delete the \Cache subdirectory. This
probably won't help, but it's completely harmless and easy, so it's at least worth trying.
(If you're running a RealFlight version earlier than Evolution, simply replace the directory name above with your version as appropriate.)
Next, try deleting or renaming your \Vehicles subdirectory. This will prevent RF from seeing and loading any custom content. If that solves the problem, you can try selectively reimporting things until you identify which one causes the problem, then either remove it manually following steps like
@asj5547 put forth above (though also check your \Vehicles\ColorSchemes and \Vehicles\CustomVehicles dirs) or repeat the above method to start over fresh once again and this time reimport only the things you know are safe.
If none of that helped, delete or rename your RealFlight64.ini and try again.
Let us know your results!
