Fred
I cannot see why this causes you a problem other than maybe the Sync Process that is happening with Dropbox is somehow causing you the issue. If you use another folder on F Drive (one that does not sync to Drop Box) does it do the same thing? If you suspend the Sync Process to Drop Box before doing this does it still do the same thing?
I dont believe the fact that TBC is on C: and the data is on F: makes any difference at all, I am almost 100% certain that this is being caused by background Synching with Dropbox in some way is messing with the data being imported in some way.
If you set up a folder on C: that also syncs with Dropbox can you tell me if this same problem occurs?
Let me know the answers to the above and then we can validate on our end - I am not sure we have a Drop Box installation and it for sure is not a part of our standard Testing - I can use the equivalent Google Drive function and see what happens there etc. once I know the answers to the above.
Thanks
Alan