Just a guess but I would suspect If you have Hydraulic steering
the problem may be with the checkvalves inside the pumpset. (Older steering
systems have external checkvalves but from your boat video I doubt you have that old of equipment) When you are going fwd there is less pressure on the rudder
hence less oil
pressure will move the rudder/ram. In reverse there is more pressure against the ram and the check valves may not be sealing correctly. This also addresses the "unlimited" turns of the wheel
The good news is that it should be a cheap
repair if you take it to a hydraulic shop.