As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - AFTER SELECTING THE GEAR "UP", THE MAIN GEAR REMAINED IN TRANSIT FOR A EXTENDED PERIOD OF TIME. WHEN PLACED TO "DOWN" NO ACTIVITY FOR 5 SECONDS OR SO. RETURNED TO THE FIELD AND ACCOMPLISHED A UNEVENTFUL LANDING. MAINTENANCE REPLACED THE BALANCE RELIEF VALVE. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.