Glitchy artifacts on Nightfall and AI bug

When i started up mission Nightfall on Legendary, when in cut scene droping from the mountain and into the game play, there are random visual artifacts on trees and rocks. Ai in sword base (Allys) when moving toward and pushing you end up making you fly a bit forwards towards were they were walking. I have a video of the Artifacts but not the Ai. https://twitter.com/Migz117/status/1203174127013711872?s=20 Video of Visual Bug.