Sometimes, StorageCraft ShadowProtect retention fails. One cause of this, is a corrupt database. There is no such warning in logs. The way to confirm, is to stop the ShadowProtect service, delete or rename SPX.DB3 located here:
%ProgramData%\StorageCraft\SPX
to SPX.SP3.OLD, restart the service, recreate both destination and job settings, and test. If the retention policy works, you’ve fixed it. Interestingly enough, when this works, it often will not need manual cleanup of the destination folder, but will take care of much or all of the cleanup of old chains automatically. Does not always happen however.