Well, I don't know if it is normal or something like, but I've been seen some mobs walking on a glitched way, but they aren't glitched, cause when we attack, they go back normal.
the most of them, and the only ones that I've seem... are the ones who are behind another mob (following), here is a video:
DBOG - Patrol Mobs Glitched (Watch it from second 0 to 20)
If it is normal and not a bug or glitch or else, amek me know and or ignore / close my post (I serached for this but I didn't find any thread with it)