As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 4228 - CREW ELECTED TO RETURN TO FIELD AFTER EXPERIENCING A P/L SPLIT IN CRUISE CONFIGURATION. PIT MAINTENANCE INSPECTED AIRCRAFT AND DISCOVERED BLEED AIR ADAPTER ATTACH BOLTS WERE LOOSE, TIGHTENED BOLTS IAW MM 75-00-00. OPS CHECKED GOOD. AIRCRAFT RETURNED TO SERVICE.