As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNABLE TO SELECT LANDING ALTITUDE. LANDING ALTITUDE FROZEN WITH KNOB SELECTOR MOVING. GROUNDED - YES. REMOVED AND REPLACED PRESSURE SELECTOR UNIT REF B737-800 AMM 21-31-02/401. PERFORMED PRESSURIZATION SYS GROUND TEST OF AMM TASK 21-31-00-700-802. BOTH TEST SUCCESSFUL FUNCTIONAL TEST OF PRESSURE SELECTOR GOOD.