How to Resolve a Duplicate Mount Point

If Mac OS X or Mac OS X Server is restarted unexpectedly, the current mount point that is listed in /Volumes may not be deleted and a new ("false") mount point with a "1" appended to the name may appear (such as "My Volume 1"). This can cause issues for Backblaze Computer Backup because the Backup Client relies on the path to certain files that are located in secondary volumes.

You can read the full article and find the fix here.