It may not be a maintenance issue.. The side to side "Rocking" you describe is called SWAY (Yup Sway means different things in a Motor home and a Trailer, on a motor home trailer type sway is "Wag") Now workhorse Custom Chassis, knows their frames are going to be RV's so they put on an oversize Sway Bar.. At least in the case of my rig it's rather effective.
But many (including WCC) the same chassis may be used for other things which are not nearly as "Top heavy" as an RV, so the sway bar from the factory is simply not up to the task,, never has been.. So if the owner is the original owner he may thing "This is normal for Motor Homes" mostly because it is as delivered new.
Where as we the readers of these and other forums, Know it can be fixed.