If your coach rocks a lot when walking around inside while parked, that indicates your suspension will benefit from some upgrades. Benefits primarily benefit "handling", but spills over into your area of complaint.
I advise to start with heavy duty Bilstein shock absorbers and heavy duty Helwig front and rear stabilizer bars, then re-evaluate.
Our rig
SEEN HERE has had lots of suspension upgrades over the years which make it handle very nicely which also improves stability while parked.