repost from russian aviation forum, supposedly it's a summary of MAK's concern:
"There are cutout switches available on the pedestal to stop a stabilizer trim runaway. It's really important that the autopilot self test is carried out regularly on the ground by maintenance. However, you can get a stabilizer trim runaway when an autopilot is engaged if maintenance has installed the elevator position feedback link in the wrong way around. This manifests itself as a nose down uncontrollable trim which, when the autopilot is disconnected again, needs to be manually trimmed out or the elevators will not be faired with the stabilizer. Remember there are stab trim lights on the instrument panel that need to be taken seriously."