As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRSPEED NUMBER IN IAS/MACH WINDOW FROZE, KNOB WOULD TURN BUT THE AIRSPEED NUMBER AND AIRSPEED BUGS WOULD NOT CHANGE. THE PROBLEM OCCURED ON DESCENT IN KSEA WHEN CHANGING FROM VNAV TO LVL CHNG. PROBLEM COULD NOT BE FIXED BY RETURNING TO VNAV. GROUNDED - YES. PERFORMED ALT DEACTIV PROC 05-07-07 TABLE 3 ITEM 1 REMOVED AND REPLACED DFCS MODE CONTROL PANEL OPS CHECK GOOD REF AMM 22-11-34.