As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT#1924, STI-BOS. (AIRCRAFT PERFORMED AN AIR TURN BACK TO STI) PRESS CABIN ALTITUDE HIGH WARNING IN FLIGHT CLIMBING THROUGH 18K CABIN PRESSURE CLIMBED TO 11'000, TEMP TO 96 F. ( MANUAL CABIN PRESSURE CONTROL SYSTEM ). REF L/P 3656598 FOR CORRECTIVE ACTION. MX-4 UPDATED. PLACARD REMOVED. MDDR CLEARED.