I stumbled upon a weird problem while modelling a wall of a building. I started with a plane, then added windows by subdividing faces (Ctrl+R) and using insets (I). Then I dissolved some edges that didn't seemed important for my model. However after dissolving them, faces started to look weird/glitchy, like they were overlapping. Apart of that, I can't select separate faces, feels like something is covering them. That's a bit counter intuitive for me since i'm working with a 2d plane so it should be impossible for faces to overlap.
When I try to extrude, I get a sort of copy of plane, not the actual extrusion.
All this makes further work on this model impossible and forces me to rollback a few steps, which isn't a big deal, but I'd like to understand what causes this issue to avoid it in future.
I would be grateful if someone more knowledgeable could explain it to me. Please take a look at the video in the link to see what the problem looks like.