This has only happened sporadically, but sometimes when I look at far away enemies (around 400+ meters), they appear to hover around, rapidly raise/lower their guns, or otherwise behave very irregularly. Their animations don't obey the laws of physics. They can still shoot at you, even though their animations don't look like they can. They don't appear to lose any functionality; it's purely visual.

If anyone remembers the fire ant glitch in Fallout New Vegas, it's kind of like that. It doesn't always happen, and I haven't been able to intentionally reproduce it.

I noticed it the most during the vehicle showcase. I was standing by the radio tower, looking at the base where I had previously destroyed the vehicles. There were still quite a few enemies alive, and they were glitching out. One of them was shooting at me, but he wasn't looking at me, and his gun was lowered. With every gunshot, his gun would instantly raise, and then lower lower back down.