As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ASH 7333 IAD. CAPTAIN REPORTED AT MACH .72 AIRCRAFT ALTITUDE OSCILLATES +/- 200 FPM AND AT .77 MACH RH ELEVATOR POSITION INDICATOR ON MFD CONTROL PAGE APPEARS TO SHOW SMALL HIGHT FREQUENCY DISPLACEMENT. MAINTENANCE REMOVED AND REPLACED ELEVATOR SERVO.