Make sure there's not too much play in the linkage. If so, the valve can spring to the wrong position as I demonstrate here:
https://youtube.com/shorts/8VWbsWP6gmA?si=QEPHdjAUHoRN6r6W Off the top of my head I don't think a valve sticking could cause this (except the manual valve for obvious reasons) since the valves need to be free for the shifts to happen.
Let's say if the Low-High valve were stuck, perhaps it could cause the opposite condition (H and D are both H) but that's not what you experienced.
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