My diff lock sticks once in a while and I can tell immediately because the front tires and the tractor slide straight ahead even if the tires are aimed completely to the left or the right. Sometimes I just need to reverse for a second to disengage it. Very rarely do I need to go back and forth more than once or twice. It only happens though, when my big clod-hoppers accidently hit the control button. It sounds like the external lever is disengaged but the button on the transaxle is sluggish popping back out.