As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRPLANE HAS PITCH OSCILLATION, PORPOISES, WITH ANY A-P CHANNEL IN CMD & V-S, ALT HOLD, FLCH, VNAV MODE SELECTED. WORSE IN VNAV PATH AT CRZ. +- 60 FEET AT ALTITUDE. ACP MCDP TEST 30 & 40 NO FAULTS FOUND. CHECKED ELEV PCA'S. ELEV OPERATIONS FOUND TO BE NORMAL IAW MM.