Sometimes some enemies (Ruby Nagasa, Sapphire Nagasa, Spine Hunter, Hollow Druant) have no walk, attack and death animation.
Desert Spitters, Desert Stingers and Phraxes can sometimes be invisible.
Sometimes this affects the whole group that spawns. Sometimes only a couple of them.
(Recorded the Ruby Nagasa. First group is fine. Second group ~4 of them don’t have animations. Third group only ~2 have animations.)
I think this happens only in the arena, because i checked some of the world maps a couple of times where those enemies spawn (except for Phrax) and it doesn’t happen there.