Did you had Offline Files enabled? The client tries to move the files from the old target to the new one.
2 ideas:
- configure Folder Redir to not move the files, see tab on each folder im GPO
- reset the CSC Cache / Offline Files Database to remove the old target from sync
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Csc
DWORD -> FormatDatabase = 1