Guy just got back to me and as usually he is pretty much on top of
this from the contest scoring side. IGC files can have either a a
GLIDERID field or a COMPETITIONID feild. The Winscore software checks
both for the competition ID.

The issue appears to be with some loggers. In looking at a selection
of files I have seen either field and some have both. The problem
would only occur if the logger only stores a GLIDERID field. It would
be interesting to know what what loggers do this but do not store the
COMPETITIONID. This would force the pilot to use the GLIDERID for the
COMPETITIONID.

Brian