A critter can get stuck in "being groomed" state by the grooming station. The other critters will be excited and wait for their turn, and the duplicant will be calling the stuck critter for their entire working shift.
Including a savefile with a stuck plug slug.
EDIT: it seems the issue fixes itself on reload, so the save is useless. Sorry about that.
Have several stables with critters
Maybe an older world?
It should happen eventually.