As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EFIS SYS, EFD1000C3 PRIMARY FLIGHT DISPLAY SHOWED ERRATIC HEADING INDICATIONS DURING A PRACTICE INSTRUMENT APPROACH WHILE CONDUCTING PILOT TRAINING. SHORTLY AFTER THE ERRATIC HEADING INDICATIONS A "CROSS CHECK ATTITUDE" ANNUNCIATION WAS DISPLAYED. WITHIN 5 SECONDS OF RECEIVING THE "CROSS CHECK ATTITUDE" ANNUNCIATION THE PRIMARY FLIGHT DISPLAY "RED XED" AND ALL ATTITUDE, HEADING, AND NAVIGATION INFORMATION WAS R & R WITH FAIL INDICATIONS. THE FLIGHT RETURNED TO DEPARTURE FOR LANDING AND EXAMINATION BY MX.