When winbind offline logon = true and a user logs in and then disconnects from the network, the user is unable to use any of the groups they are a member of since they aren't yet cached. Running 'groups' results in lots of errors that the group ids couldn't be resolved.
If winbind offline logon = true is set, when a user logs in each group (primary and supplementary) should be looked up so that it gets added to the cache (making sure that both forward and reverse lookups work).
Thanks for this bug report.
Right, it might add value to the offline mode when winbindd
would proactively fetch and cache certain data like resolutions
of the user's groups. Possibly doing so _only_ when "winbind offline
logons = yes", since it will also slow down the processes that don't
need this information.
I'll have to think about what to fetch when best....