Save A as B, CAN NOT open A and B in different axure

bug repeated as follows:

  1. Open an existed file A and save it as B, edit on B and save it;
  2. A and B is different file indeed, but stored in a same folder;
  3. Open file A first in axure, then open another axure application and plan to open B in this one;
  4. Warning dialogue shows an instantce has been opened in axure, then B can not be opened.
    If copy B to a different folder and execute the procedures 3 above again, this thing won’t happen.