It might be a circuit problem, but here's my two cents worth.
I've seen a lot of problems with the push-button switches on the 2200 series scopes.
Before tearing into the circuitry, try playing with the push-buttons.
Make sure they're locking-in when they're supposed to, and releasing when they're supposed to.
Might not help, but it's isolated the problem for me quite a few times.
good luck.