Missing Face Crash

[micheus]

Missing faces shouldn't​exists, except by creating wrong topologies.
If you need a hole you must to use the proper command for that. If you need "single" face grouped you must to use extract or extrude without thickness. Wings3D needs a manifold surface and it try to keep them that way, but sometimes we are able to "workaround" this and it creates wrong and inconsistent objects.

I suggest you to try Cleanup in body mode. It can sometimes"breaks" your object, but can fix internal inconsistencies.

Please try that and give me a feedback.
Also, if you can, attache the Wings3D' project file causing the crash because it uses to be hard create broken meshes like this by our own.