As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOST PRESSURE IN CABIN AND RECEIVED A SERVICE DOOR MESSAGE. (FLT 5603) INSPECTED SERVICE DOOR CUTOUT & EXTERNAL, FOUND NO DEFECTS. OPERATIONAL TEST OF CPCU 1 & CPCU 2 IAW AMM, PRESSURIZED AIRCRAFT ON ENGINE BLEED ON BOTH CABIN PRESSURE CONTROLLERS ONE AT A TIME WITH NO LOSS OF PRESSURE AT DELTA-P 4.0. OPS CHECK GOOD.