Escaping Essence monsters

Had a "Flesh Larva" monster essence in Mud Burrow, all of the monsters were able to escape the crystals when I got next to them, and damage me, but were completely immortal. Couldn't target them, and no abilities would touch them.

I have seen some monsters move while trapped, but this is the first time I have seen the monsters completely escape and even chase me around.

Was in cruel act 1 on ps5 pro