As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ETOPS SIGNIFICANT SYS - CAPTS ALTIMETER HAS UNSTABLE READOUT (-100 TO 200 FT) IN CRUISE FLT AT FL380 SWITCHED CAPT TO ALTERNATE AIR DATA AND READOUT STABLE. R & R CAPTAINS ADC IAW AMM34-12-01. DID MCDP TEST 30, NO FAULTS NOTED. OPS CHECKED GOOD.