The doubling of correct statements might be a bug in draggableProof.pl. I've noticed that it doesn't work well when you use randomizeProblem to give a new version (the items in the right column don't get erased). You may be seeing a different version of the same phenomenon. I suspect this doesn't happen with a freshly assigned problem.
If you can collect data on what makes this doubling occur it will help with the fix -- but I can't guarantee when the fix will occur.