As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
A 70 KT DIFFERENCE BETWEEN CAPT & F/O MACH VMO FLAG INDICATOR. CAPT SHOWING 250 & F/O SHOWING 340 AT FL 260 MACH WARNING HORN WAS GOING OFF. ATB MHT. T/S SYSTEM PER TAFI 34-13-00 REPLACED NR 1 CADC AND MACH AIRSPEED INDICATOR. CLEANED PITOT LINES WITH NITROGEN NO OBSTRUCTIONS FOUND. PERFORMED PITOT TEST OF SYSTEM BOTH CAPT & F/O INDICATORS CHECK NORMAL. RETURNED TO SERVICE.