As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT DECLARED MECHANICAL EMERGENCY. FLT RETURNED TO FAR. CLIMBING THROUGH 9000-10000 I NOTICED CABIN ALT 7500 RATE 500 FPM TO 1000 FPM SOMETIMES IN AMBER RANGE. MAX DELTA P WAS 7..8 UPON LANDING. THE CABIN ALT MAINTAINED 7500. RATE WAS ERRATIC. EICAS MESSAGE PRESN AUTO FAULT-C/A-PERFORMED FIM TASK 21-31-00-810-819-A. REMOVED OBSTRUCTION FROM OUTFLOW VALVE. OPS CHECK GOOD. AIRCRAFT OK FOR SERVICE