Imps are behaving like they were trying to do something else than returning to Storage Room to put there held item. If you click on any Imp that holds an item you'll see that it's status changes from Returning to Room to Idle, but for a split second, than returns to Returning to Room status.
Save file: link
Map seed: 98765
Level difficulty: Easy
Save file: link
Map seed: 98765
Level difficulty: Easy
Spec: Win 10, ATI 7800 HD, res: 1280x1024x75. I support The Venus Project & Resource-Based Economy