As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER GOING THRU FL200 WE RECEIVED THE CAUTION WARNING THE ALT DISAGREE WAS INTERMITTENT AFTER FIRST OFFICER SIDE WAS VERIFIED TO BE CORRECT RAN QRH MAX ALT DISAGREE WAS 500 FEET REFERENCE PREVIOUS UPDATES, THIS AIRCRAFT PASSES ALL AMM TESTING WITH NO FAULTS FOUND, BUT STILL REQUIRES WAVINESS CHECK. THIS ITEM CLOSED AND SEPARATE ITEM 20-01 4367 FOR WAVINESS CHECK CREATED.