Deleting certain points then undoing breaks the validity of path

3.0.4 (3097)
I haven’t figured out how to reproduce it but sometimes when I undo, the result isn’t what I expect, it looks like the path is invalid – like a path should have a point somewhere but it isn’t represented or only a control point is visible at a on-curve point. Will try catch how to reproduce it.

Do you have hints or corner components in those glyphs? Or did you swap with the background?

No hints or corner components, I might be using the symmetrify script by @TimAhrens at some point in my undo history. Not sure yet.