Cannot Bind Spectre for Brimstone Crab

Unlocked bind spectre, went back to the Vastiri Outskirts, and tried to bind a Brimstone Crab, but it never gives me the option.

Can use other corpse skills on their corpses. They were white enemies. Made sure to get a corpse that wasn't overlapping something else. Can't think of anything else that would be causing a conflict.

Similar issue with Boulder Ants at The Halani Gates.