As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) WHILE CLIMBING THROUGH 7200 FEET, THE CAPTAIN WAS MAKING SMALL INPUTS TO STAB TRIM. MACH TRIM CAUTION MESSAGE APPEARED FOLLOWED RIGHT AFTER BY A STAB TRIM CAUTION. THE STAB WAS NOT RESPONDING TO INPUTS. PILOT TRIED TO RE-ENGAGE THE STAB AND NEITHER CHANNEL WOULD. AIRCRAFT RETURNED TO BASE. THE LANDING WAS UNEVENTFUL. FOLLOWING TROUBLESHOOTING, MAINTENANCE REPLACED THE MCU AND THE NR 1 SSCU. AIRCRAFT RETURNED TO SERVICE.