Why is samba with ldap backend (ldapsam) ignoring secondary group memberships?

Issue

• Using a samba share, access to directories is restricted with groups. Samba seems to honour only the users primary group membership, directories that have on linux level memberships so they should be accessable via group permissions are not accessable via samba. Attempts to access the directory that should be accessable via secondary group membership leads to the following message in the samba logs:

check_reduced_name: couldn't get realpath for directory/*