I bought the New Vegas ultimate edition when it went on sale on steam. I own it on ps3 but I wanted to get it on steam so I could get some mods. I started up a game with some mods and when i first met Doc Mitchell his head what twisting around upside down and when he got up from his chair he just floated around in the seated position. When I went into goodsprings everyone was not doing the walking animation, but instead floating around. When I encountered the geckos they did the same thing. I uninstalled and reinstalled the game 3 times and it still does this glitch. Disabling the mods did not help either. Is there anyway to fix this? Thank you in advance

When you uninstall the game you need to make sure you manually delete the fallout new vegas directory in the steam folder after deleting the local content in steam. I would also delete the directory with your saves (the entire directory it's in along with the 2 ini files). You can backup you saves first.

Install the game only first. No mods. The DLC is fine.

See if this happens pure vanilla. Start a new game.