I called a GM about this problem a long time ago, and they said it was due to lag, even though it was quite obvious that the monster pathing was screwed. =\
This proves that GMs DO PLAY AS MOBS!
As they are playing as a mob, they are getting lag, like we are, and move randomly- BYMISTAKE!
I think I'm on to something!!O_o
"In war, truth is the first casualty."