Yes the AutoPark can be problematic. There is a fellow who has a website devoted to that system. Is it oldusedbear? Read all about it. Parts are getting hard to find and very expensive. If the system fails and applies the brake while you are driving unless you stop immediately it will be at least $1500 to repair. I have owned an older unit (96) and a 2004. Different systems. The older one is easier to fix. A pump for the newer one is about $1500. On the new system a new cylinder that applies the brake is over $1000. As much as I am a Chevrolet fan since Workhorse bought the rights to the P32, sold the business to Navistar and then it closed, parts are very expensive. Not much aftermarket stuff. You can still get tie rod ends and ball joints from Moog. Shaft kits are harder to find. Drag links have to come from Ultra or Henderson and are about $230. Bellcranks are only available from Super steer . No one sells rebuild kits for these. The front ends are weak. If you have a short unit with a short wheelbase be prepared to spend between $3000 and $5000 for a rear trak bar, 2 bellcranks, new springs and more.
Moisheh