As I understand it your step motor works fine when not connected to anything, your steps open/close when not connected to anything. But when you put everything together the steps will extend but wont' retract - is that correct?.
Have you tried lubricating everything? Have you visually inspected everything to insure that something didn't get bent out of line when you had your air suspension issue?
For what it's worth - the vast majority of step issues are associated with low/bad battery and/or corroded ground wire from the step. Suggest you check both just to rule out the obvious.