This from the Steve London, N2IC, on the N1MM Reflector. Word to the wise and all that rot. Emphasis added by me.

73, Ken K3IU

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I recommend taking a look at latest entry in the CQWW blog, written by
CQWW director K5ZD. See http://cqww.com/blog/?p=50 .

In particular he makes this comment:

“There is one very popular software package that does not always correct
the zone number when the call sign is edited. This can result in zone 35
being assigned to a station in Germany or 13 being assigned to a station
in Japan. This will result in a lost QSO when we do the checking.”

I suspect he is talking about N1MM Logger. This issue can easily be
rectified by properly setting one option in N1MM Logger. In
Config->Configure Ports->Other there is a check box “Clear populated
exchange on callsign change”. This should be checked for CQWW (as well
as many other contests).

73,
Steve, N2IC