As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: AT FLIGHT LEVEL 390 WITH FLIGHT LEVEL 210 SET IN ALTITUDE WINDOW, MANAGED DESCENT SELECTED. AIRCRAFT INITIATED CLIMB. VERTICAL SPEED SELECTED TO REGAIN DESCENT. AIRCRAFT REACHED FL 394 . NO OTHER ISSUES IN DESCENT. MAINTENANCE ACCOMPLISHED AFS OPERATIONAL TEST PER AMM 22-96-00-710-001A. TEST PASSED. ACCOMPLISHED FCU OPERATIONAL TEST PER AMM 22-10-00-710-006A. OPERATIONAL CHECKED GOOD.