As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK: IN FLT (7584) FROM RAP TO FSD; ENGINE NR 1 AND ENGINE NR 2 DE-ICE FAULTED, NR 2 PROP ANTI-ICE FAULTED AND AIRFRAME DE-ICE FAULTED. AIRCRAFT RETURNED TO RAP AND LANDED WITHOUT INCIDENT. AFTER TROUBLESHOOTING, MAINTENANCE REMOVED AND REPLACED NR 1 ENGINE DUEL DIST DE-ICEING VALVE AND NR 1 DE-ICING CONTROLLER.