Copying 84 gigabyte file via USB results in duplicate file warning and case sensitive fail where no duplicate exists I'm attempting to copy an 84 Gigabyte photo library from an external Case-sensitive Journaled HFS+ disk to a newly formatted case-insensitive APFS SSD. The external disk is in an external drive bay connected via USB.

The operation takes a few hours, at which point I'm greeted with the error message


  You can’t copy this file because its name is the same as other items on the destination volume, and that volume doesn’t distinguish between upper- and lowercase letters in filenames. 


There is no duplicate file on the drive. 

Is the file name being cached somehow because of the file size? Is it something in the package contents? The file integrity is fine - I can open it as a photos library from the bay. I thought I could open it as a referenced file and use the Photo's Consolidate option to simply get around the issue, but "Show referenced file" and "consolidate" are both greyed out in the file menu. 

Can I use rsync or some other method to copy the file or are there actual case-sensitivity issues in there I need to address? It's my wife's entire photo collection, so I'm proceeding with extreme caution, and would greatly appreciate guidance.
OP's solution:


  in the end opened up my FTP client and transferred the file via my local ethernet. It worked!






  I would highly recommend that you perform a total system backup using Carbon Copy Cloner.
  
  Carbon Copy Cloner does support restoring to a case-insensitive system from a case-sensitive one - see this.


https://superuser.com/a/380358/1038202

  SuperDuper is the best way to clone drives in OS X. You can rename the destination drive in Finder


https://superuser.com/a/20779/1038202
There's also a script on Github, which claims to 


  
  Resolve all case-sensitivity naming conflicts
  Make a fresh TimeMachine backup 
  Flip the backups's case-sensitivity flag 
  Restore from the manipulated backup
  


https://github.com/cr/MacCaseSensitiveConversion