As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING CRUISE AT FL 350 AND IN DESCENT TO APPROXIMATELY FL240, THE V/S FT/MIN NEEDLE FLUCTUATES FROM -650 TO +150 WITH OUTFLOW VALVE NEEDLE MOVING. ACCOMPLISHED OPS TEST OF SAFETY VALVES POSITION INDICATOR PER AMM 21-31-00. ALL CHECKS GOOD. REMOVED AND REPLACED OUTFLOW VALVE 10HL PER AMM 21-31-51.