Some other customers have reported a similar issue, but it's always sporadic and we can't target it to any particular drawing to check what is going wrong.
When any CSD command is run in a drawing, then the software 'flags' the drawing as requiring a -Data folder (this is written in the drawing 'dictionary' and is saved with the drawing). If you then save that as a .dwt or a blank .dwg for other purposes, every time it's opened and saved, the software will go ahead and create a -Data folder because it sees this flag and thinks it's required.
You can go to any .dwg and run the command arduv7RemoveARDRunFlag. That will remove the flag and stop the behaviour.
If you think this problem may be in your .dwt, then
1. Create a new drawing from the .dwt and save it as a .dwg
2. Run the command arduv7RemoveARDRunFlag
3. Do a Save As and save as a .dwt - overwrite the current .dwt.