MC-8s & 9s are notorious for "cornering on the rub rails" because the factory did not install any anti-roll bars in the suspension system.
So it takes a little bit before the leveling valves respond, and then a little bit more for them to bring everything back.
Mark's comments are valid - may be a cruddy valve on one side.
Leveling valves are relatively (for a bus) inexpensive, once replaced, with good system maintenance you'll probably never have to do it again.
FWIW & HTH. . .