This issue is fixed in System Software 1.1.0.
When running UEFI diagnostics on the server from Oracle ILOM (under Host Management > Diagnostics from the web browser user interface), do not attempt other server-related actions, such as firmware update or a user-initiated server power off, until diagnostics have completed and you reset the diagnostics mode back to disabled in Oracle ILOM under Host Management > Diagnostics. Doing so can cause firmware corruption during the diagnostics tests.