Missing Face Crash

[micheus]

Did you tried to bring back the hidden face as I told you in my previous post - see "edited".

Let see if I can explain it better or make you more confused...

When you hide a face or mark it as a hole Wings3d will still keep "its information". Think like the face was still there and as it works for regular face, when you divide it with cut one of the two faces keeps the original I'D - you can think this as the original face getting a small size and the "opened hole" being closed with a new face.

So, you are cuting/connecting edges own by the hidden face/hole and Wings3D is trying to keep it. If you didn't need a hole you need to know that you need to remove it before do this kind of action.
If Wings3d just ignored that and them closed the hole automatically, one could say: "but, I was just trying to reduce the hole, not remove it".

It's our call tell to Wings3D what we want to happen and we do that planning our the actions.