Yes! I've had that happen, too. Sometimes the arm on the back of the knuckle wears down or the end breaks off, and it no longer hits the stop inside the coupler head. When this happens, the knuckle can open too far and allow the ball bearing to fall back down on the wrong side of the arm, locking the knuckle in the open position. Flipping it upside down, or using the magnetic wand will pull the bearing back out and allow you to close it, but truly fixing it usually means disassembling and replacing the knuckle.