We have a Winnie Outlook 29B, 30 feet long. We get the same experience you have when 1) front tires are overinflated. Michelin guide recommends 65psi for our weight, we run 70psi. When shop inflates to 80psi (sidewall max) we have problems. 2) We have auxillary rear air springs and when they lose pressure, handling is adversely affected, I try to maintain 70psi in the airbags.
Try these measures first, cost almost 0 dollars. If your still having problems then do as Donn0128 said, take it to good alignment shop that work on heavy vehicles, have them inspect the chassis for worn or broken parts.
Make and model of tire can also affect handling, ours improved when the factory Michelin LTXs were replaced with Michelin Ribs. I actually prefer driving the MH on the highway over the CRV.
Beverley and Ken