As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ETOPS SIGNIFICANT SYS - BOTH PNEUMATIC PRESS DROPS EXCESSIVE WHEN LT & RT PACK SWITCHES ARE TURNED OFF USING BOTH APU OR ENG BLEED AIR (BLEED AIR DOES NOT RETURN TO NORMAL) REPLACED LT FLOW CONTROL VALVE IAW AMM21-51-01 TILL STEP 4A. OPS CK IAW AMM21-51-01 OK.