That's weird. Did you ask Wacom's support about this issue? Maybe there is a driver update, for example.
I wouldn't be too hard to check for duplicates like this, but I'm not sure I should. If it's Wacom's bug, they should fix it.
Unfortunately I don't have a Wacom tablet to test with, but see if you can reproduce the problem in Interarchy, for example, or any other FTP app that will allow more than one simultaneous transfer. Fetch and Captain FTP will not.