As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MCP ALT WINDOW FREEZES. WILL NOT ALLOW YOU TO RESET THE ALT. ACFT GROUNDED. REPLACED MCP REF MM 22-11-34-400-801. MCP INSTALLATION TEST OK. REF MM 22-11-34-740-801. ETOPS GROUND VERIFICATION COMPLETED BY ALSO DOING THE MCP FULL EXTENDED MAINT TESTS. ALL TESTS PASS. DID A FULL SWEEP OF THE ALTITUDE WINDOW.