I'm still using Adobe 2020 (2021 never seems to launch, even after validating my fonts), but I had a weird issue that cropped up that I've never seen before.
I set up a clipping mask outside the border of my project to capture the edges and clean my board up a bit. When I went to move some of the items within the clipping mask (with the direct selection tool) it occasionally highlighted some of the items but wouldn't select them or let me move them. Everything was unlocked, only working on one layer. Despite showing on the screen, it behaved as if those weren't there. When I moved the image, it changed the clipping mask to one of the smaller items I had, though it wasn't showing that way initially and that isn't the right item that had initially contained the clipping mask.
Has anyone had this happen to them? What did you do to fix it?