Show cut sites when enzyme located on junction point

Scenario:

1. Open attached "example.gb".
   Expected: sequence is circular.
2. Click "Find restriction enzymes"
3. Choose "Tth111I".
4. Click OK.
5. Open details view.
   Expected: enzyme has cuts.
   Current: enzyme does not have cuts.

Note: I started doing this, some code I have already written (see attachments).