As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
((X1IR)) ACFT OWNER COMPLAINED OF PRESSURIZATION PROBLEM AT FL 290 WHERE THE CABIN PRESSURE WOULD INTERMITTENTLY DROP FROM 6.2 TO 4.0 UPON INVESTIGATION, FOUND THE ACFT DID NOT SWITCH FROM 3.0 TO 2.5 BLEED AIR. CAUSE IS DETERMINED, DUE TO THE SHUTOFF VALVE HAVING A METALLURGICAL PROBLEM WHERE THE INTERNAL SHUTTLE VALVE SEPARATED, WHICH MADE THE PART NOT OPERATE PROPERLY. THIS PART OPERATES AUTOMATICALLY AND REQUIRES NO INPUT FROM THE ACFT OPERATOR.