I worked on them years ago. I'd guess the hard drives are ok if they've been turned off/on, or restarted. I can't recall any no header situations when I worked for Rolm on the 9751s (did with 8000s) unless the hard drive was n/g, but I think we'd at least see a prompt to insert the CNFG diskettes.

I do recall if the serial output paused during a session, Ctrl-Q (opposite of Ctrl-S) would sometimes 'unpause' the output.