I noticed SketchUp starts to behave strange when there are a lot of lines on a simple 2D plane. It doesn’t always divide faces on the plane with lines, instead creates multiple faces overlaying themselves. Sometimes removes the face of the plane when a line inside of the face that don’t touch the borders are removed. I’ve been Using SketchUp for 12 years and I can’t see anything that I might be doing wrong. It’s just acting like it shouldn’t in random cases.
Can you post a model that displays what you describe, with instructions how to reproduce?
Does it happen if you turn off Length Snapping? Length snapping, with the numerous “from point…” type inferences can create geometry that is ever so slightly out of whack and could be the source of this