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#21
Stevekir.
Those .FFS_TMP files are associated with your Free File Sync program. Refer to this website.
FreeFileSync / Discussion / Help:Orphaned .FFS_TMP files in target directories
Unfortunately they don't say how to delete them.
What version of FFS are you running, it seems that later versions permanently delete the .ffs_tmp files. I think from what I read on the web it was version 5.21.
It might be worth using the FFS support or help to see if they can help you.