This error means that the application's local repository (cache) is corrupted or invalid.
This most commonly occurs after an update or when the application was not closed properly.
How to resolve the issue:
Close ABRA Flexi
Delete the cache folder:
Windows:
C:\Users\{user}\.winstrom\cache\
or
C:\Users\{user}\AppData\Roaming\.winstrom\cache\
macOS / Linux:
~/.winstrom/cache/
Restart the application