As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FOLLOWING HEAVY CHECK MAINTENANCE DURING CLIMB OUT CREW HEARD A LOUD POP THEN CABIN BEGAN TO DEPRESSURIZE. CREW COMPLIED WITH QRH AND REDUCED ALTITUDE AND DIVERTED BACK TO OKC FOR INSPECTION. FOUND SERVICE DOOR SEAL WITH NO VENT HOLES, CUT HOLES IN SEAL IAW AMM 52-41-07, PRESSURE CHECK GOOD