On a Plinth there was a Health bottle and on another a gem, I picked up the gem from the side and out shot several spears and then retracted but with the Health bottle when I took that, arrows started shoot out but the did not stop, the "button-trigger" the bottle was sitting on never stopped moving quickly up and down so the arrows never stopped.
This might not be a bug , but all other "plinths" the Button Trigger goes down when you take the item , that triggers the trap-weapon but the button-trigger moves back up to the default position and that retracts or stops the trap-weapon. But that is the first time I;ve seen the button-trigget on one of these plinths move rapidly up and down and not stop.