I would check for front steer cylinders bypassing first. All u have to do is start the lift. Put truck into side mode. Extend the front clinders all the way and rotate the steering wheel one full turn on the pressure relief. Then retract them all the way and rotate the steering wheel one full turn against the relief.

Change the mode from side mode to forward mode. Then back to side mode. Let the truck move the front steer cylinders to 90 and stop.

Now that the system is bled again go to the right hand side of the truck. This is the master cylinder. All Combi's with this steering system are all made the same and will always have the master on the right hand its also physically bigger.

Take the front hydraulic hose off of the cylinder. Cap and plug the hose and cylinder. Mark the chrome rod of both cylinders with a line approx 1in away from the cylinder end. (Use a measuring tape to mark)

Now with the truck running and in side mode turn the steering wheel at least one full turn each direction. Then check the steer cylinders.
If either cylinder has extended (mark has moved outwards) that clkinder is bypassing and will need to be replaced.

Most of the time one will be bad and the other still okay. Sometimes both are bad.

If both cylinders show to be good. Make sure the master cylinder (rh) is adjusted properly and that the stop bolts on the deck are properly adjusted. These need to be adjusted for the purge valve in the master cylinder to work properly.

These trucks do drift when the key is shut off or dierection lever is placed into neutral as hydraulic pressure creeps through the valve but the truck should move them back into position when a mode is selected. And I believe there is a one way check valve that prevents this on the new trucks installed near the 6 port steering valve. But im unsure of your truck has this.

I have also heard of the 6 port steering valve causing this from other techs but have not personally seen it myself.

Bleed procedure is just all the way in and then all the way out several times. No need to crack open lines.

Hope this helps at all.