As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX FLIGHT NR 2527: CAPTAIN SIDE ALT FAIL MESSAGE AFTER PUSH BACK. AIRCRAFT RETURNED TO GATE. MAINTENANCE REPLACED BROKEN RING TERMINAL AT GROUND STUD GS15 IAW Q400 SDM 34-11-01, SHEET 2 OF 8, PAGE 2. ICP OPS TESTED GOOD IAW MTC 6316103. AIRCRAFT REMAINS CAT III QUALIFIED. PLACARD REFLECTS CAT III. MTX CONTROL HAD BEEN NOTIFIED. AIRCRAFT RETURNED TO SERVICE.