240 hours in, I got my first serious glitch. None of my weapons damaged any opponent - at all. Changing weapons did not help. Loading a quick save did not help. What fixed it for me was quitting out of the game completely. It was fine after restart. Hope this helps someone.
Yeah. Best thing to do when you start getting glitches is just stop the game and then restart it. Also, make sure you have plenty of back up saves in case that doesn't fix it.