> after executing all possible combinations of "gfix -m", "gfix -v"
> still reports "Number of record level errors: 1", and "gbak -b -g
> -i -v ..." still does not get over "starting transaction".

I don't have any idea what happened, but suddenly the backup *did*
work. This completely toils my understanding of why - after a clean
reboot of the server and all users disconnected - a command would at
first not work, but then suddenly would when just trying often enough.

So, I made a backup, restored that to a new database, and this one
seems to work so far. I hope there are no hidden surprises.