[Coco] bug in latest "backup" command?

[Chuck Youse]

Has anyone ever run into problems using backup with a single drive under
NitrOS-9?  I had an odd error earlier, which I didn't spend much time
investigating -- I was copying a 40-track DS/DD floppy with "backup" on
a single-drive system. 

In any case, on the last read of the source floppy, backup appeared to
want to read beyond the end of the disk - I was getting "error #247"
when it tried to read sectors $5A0, $5A1, etc... which of course aren't
valid sector numbers on a 40-track, double-sided, 18 spt disk.

The command I used was

backup /d0 #48k

Anyway, is this a known issue, or has no one ever seen it before?  If I
can repeat it I will poke into the code and see if it's a bug.  Could be
user error, but I don't see how I could have screwed this up.

It wasn't a big deal, as I just copied the disk image and then used
backup with the 'f' flag to write it back out (much easier on a
hard-disk system, anyway).

C.