Strange error with mairix and a maildir stored by mutt

[Chris Green]

I use maildir with mutt and mairix, I changed from mbox several months
ago.

It has been working reliably for all these months.

However I'm now getting a rather odd error on one particular message
when I search using mairix:-

    chris at esprimo$ mairix 183493
    stat '/home/chris/mail/folder/shopping/food/wine/cur/1612869077.1202519_3.esprimo:2,S': No such file or directory
    Matched 2 messages
    chris at esprimo$ 

... and there's only one mail message stored in mairix's "found"
destination.

Looking at /home/chris/mail/folder/shopping/food/wine/cur I see
there's a file 1612869077.1202519_3.esprimo:2,RS which should be the
one that mairix finds.

So can anyone suggest what's going wrong?  Is it simply a bug in
mairix (in which case I'd better go off and ask in that direction) or
is there something more subtle going on to do with the ,S versus .RS
suffix on the filename?

-- 
Chris Green