wipers

When this happened to me it turned out to be a loose nut on the back of the motor. There are two bolts that attach the motor to the front cab. the nuts are hard to access but not impossible. Look under the hood and feel the nuts to see if they are loose. You can re position the motor where you want it to get the wipers to stop where you want then tighten the nuts while someone holds the bolt heads on the outside.

Check for worn out nylon or brass shoulder washers at all pivot joints.

Did you check to see if there are any missing screws or bolts that attach the motor to the MH body?
Also, check for a broken bracket or weld.
It should be a fairly easy fix.