What can cause a bad object?

I am doing

Analyse>Diagnostics>Check Bad Objects

on a file and I get an object selected. I do

ZoomNonManifold and there are no nonmanifold edges.
I Analyze>Edge Tools>Show Naked Edges and there are no naked edges.

What else do I need to check?

Or I rephrase:

What would be sequence of diagnostic steps?

Here is a Wiki page with some info… It’s a relatively complex subject. --Mitch

Thanks much. That was the kind of thing I was looking for. That’s the reason I did not post an example. I wanted to find something (like that) that would address the general problem. In fact, I was able to fix the problem