What you saw with x3dna-snap --cleanup should not happen, as demonstrated with my previous response. I am puzzled.
Could you try SNAP on another Linux distribution, e.g., Ubuntu, to see if you still get the same issue? Better yet, run SNAP on Mac OS X and Windows to see if you get the same result as you did on linux Mint 17.
I do not have access to linux Mint 17 yet, but I will try to install one to reproduce the issue.
Xiang-Jun