I assume you are talking about the van leaning when it is empty. You haven't left a lot of gear on one side have you?? Seriously, if all the kitchen equipment is to one side then that can give a slight imbalance. The other thing is the shock absorber on that side may be worn and the other possible problem is the axle suspension is worn. As long as the suspension has enough available travel to operate then it is more of an irritating problem, however, it may be wise to get a dealer with a good workshop to have a look.