As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLIMBING THROUGH 18000 FT CABIN STARTED TO CLIMB, UNABLE TO CONTROL IN AUTO OR MANUAL. DESCENDED TO 10000 FT, CABIN LEVELED OFF AT 8000 FT. RETURNED TO AUSTIN. CORRRECTIVE ACTION: INSPECTED PRESSURIZATION SYSTEM FOUND DEBRIS IN OUT FLOW VALVE, REMOVED DEBRIS FROM VALVE OPS CHECK NORMAL.