As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ACFT DEPARTED AND UPON SELECTING GEAR UP THE NOSE GEAR INDICATED UP/UNSAFE/UP/UNSAFE REPEATEDLY. THE HYD CIRCUIT BREAKER WAS PULLED AND THE EMERGENCY LANDING GEAR DEPLOYMENT WAS USED SUCCESSFULLY. ACFT RETURNED. DURING TROUBLESHOOTING IT WAS FOUND THAT THE LANDING GEAR ACCUMULATOR WAS LEAKING NITROGEN INTO THE HYD SYS CAUSING THE HYD PUMP TO CAVITATE. A REPLACEMENT ACCUMULATOR IS ON ORDER.