Flesh Larva essence monsters in Devourer's Cave spawned before essence activation

The large worm enemies in devourer's cave in cruel act 1 are untargetable for me on cursor and cannot be hit by my crossbow abilities. They were part of an essence mob and had spawned before I triggered it. While spawned they were able to damage me but I was unable to damage them.

Once I ran past them and triggered the essence, I was able to hit them

bug report 3,687,441,673