Filesync seems to alter all files it reads

[Dondadda]

I'm using Filesync to keep Serato music files up-to-date between a pc at home and Mac that I use for dj purposes All syncs are done via an external 64GB thumb drive. Syncing works well except that every time I do a sync, the Serato software "loses" all of the music files and has to "relocate lost files" after every sync. This implies that during the read or analysis process of the sync, FileSync alters the music files in some way because they ALL have to be rescanned within Serato software after each Sync.
To be clear, I only need to sync in one direction, from the flash drive to the Mac. Simple copy and paste is not the solution because the music is of different genres and goes into various different folders, which would take hours manually.
Is there a setting that I should be using that I'm not aware of? I'm currently using the Update variant instead of the Mirror variant within FileSync. Would Mirror be better for my needs?