Hello psychok9, I have a similar situation in trying to bulk copy unencrypted files to a Boxcryptor drive. Sorry, no fix (yet).
In my case the backup programs lock up. I have a folder hierarchy of unencrypted content. Sometimes, I need to maintain a local copy of files (e.g., Quicken perceives boxcryptor drive as network and unsupported). I want to use a backup utility to periodically copy these unencrypted files to a protected Boxcryptor location, so at least my backup is encrypted. This seems like a simple matter of specifying my Boxcryptor destination (e.g., X:\SecureData) in my backup client. However, both "Second Copy" and "Xcopy" have had issues. On Win 10 20H2, the backup applications locked (non-responsive, local drive spins). Anyone else find recurring success with bulk copies in Windows 10 to a boxcryptor destination (which can be cloud or NAS)?