As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON THREE SEPARATE OCCASIONS, THE MCP ALTITUDE SELECTOR WAS SET TO A NEW ALTITUDE AND THE ALT INTV BUTTON WAS PRESSED. ON ALL THREE OCCASIONS, THE CRZ ALT THAT APPEARED ON THE CRUISE PAGE IN THE FMC DID NOT MATCH THE MCP SELECTED ALTITUDE, IT WAS DIFFERENT BY 1000 FEET. GROUNDED - YES. PERFORMED B737-800 AMM TASK 22-11-00-740-801, DFCS OPS TEST. NO FAULT NOTED. CHECKED GOOD. OPS NORMAL.