As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BZN - AIRCRAFT RETURNED TO FIELD WHEN THE PITCH TRIM AND AUTO TRIM CAUTION LIGHT ILLUMINATED AT APPROXIMATELY 8500 FEET. AUTO PILOT WAS OFF. MAINTENANCE INSPECTED THE AIRCRAFT AND COMPLIED WITH SERVICE LETTER 8-400-SL-27-003 ATA 2730. OPERATIONAL CHECK WAS GOOD AND NO CAUTION LIGHTS OR MESSAGES WERE NOTED BEFORE OR AFTER THE OPERATIONAL CHECK. THE AIRCRAFT WAS RETURNED TO SERVICE.