Don’t Undo (Cntl-Z) or Redo (Cntl-Y) a Copy/Paste or Delete of one or multiple nodes. We haven’t coded the object model the GunnShow Visio plug-in to handle those actions so the results are varied and usually bad. Depending on what combination of these actions & objects you do, the node numbers and the network’s node count go wrong, and it’s very hard or impossible to recover.

We have a bug report on this here: #319, and we may actually fix this someday.

• Avoid using Undo/Redo on nodes altogether. There’s no reliable & consistent way to recover from the carnage that ensues.
• If you want to undo the addition of nodes, then simply select them and delete them individually or as a group. Verify the network’s Node Count updates accordingly as you go.
• If you want to undo the deletion of nodes, then re-add them individually by copy/pasting from other nodes or dragging a new one from the shapes library as usual.