From Valve Developer Community
SetPositioninput and Start Position keyvalue do not perform any bounds checking, so values less than 0 and greater than 1 can be used. Negative values will move in the opposite direction to the movement direction, and values greater than 1 will move it in multiples of the set Move Distance. Moving past the opened/closed position does not trigger the
Bug: There are bugs that may arise when parenting this entity to any of these:
func_doorcan be used as a workaround. See here for a code fix.