id -G (groups) inconsistency

Perhaps this is more well suited as a bug report to the sh-tools developers, but I'm interested in whether someone else has experienced the following behavior from the groups command? (Same with id -G[n]) chrisand@torvalds:~> groups chrisand chrisand : cs wheel uucp dialout audio video frej eda260 coach chrisand@torvalds:~> groups cs wheel uucp dialout audio video frej eda260 coach coach frej eda260 (Strange doubles in the second version, where user name is not given as an argument. The first version is correct, there are no doubles in the /etc/group file. The machine uses NIS as server and client, 'ypcat group' neither reports any doubles.). -- Ch