As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB OUT WITH THE AUTOPILOT ON IN SPEED MODE (IAS) THE SPEED BUG MOVED ON ITS OWN FROM 290 KTS TO 72 KTS, AIRCRAFT BEGAN UNCOMMANDED AGGRESSIVE CLIMB. FLT#5157 FOUND NO ENTRIES IN MDC FAULT HISTORY FOR AUTO FLIGHT SYSTEM ON THE DATE OF THIS EVENT. AUTO FLIGHT SYSTEM OPERATIONS CHECKED GOOD AT THIS TIME.