As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ON THE GROUND, VNAV DISSENGAGES AFTER 15 SECONDS, LNAV DISENGAGES A FEW SECONDS AFTER. ACFT GROUNDED. VERIFIED DISCREPANCY, PERFORMED DFCS BITE IAW AMM 22-11-00. PERFORMED DFCS LRU REPLACEMENT TEST IAW FIM 22-11, TASK 802. ALL TESTS PASSED. SYS RETURNED TO NORMAL.