I saw an older thread on something a bit similar, but it was with 1.3, so I don't think it applies. When I go in as a member of group and then click on the "Forum Directory" link (see screenshot) it gives me nothing. When I go in as a group mod/admin I see all the topics just fine.
It doesn't seem to be acting as it should unless I am misunderstanding what it means by forum directory, but I don't think so given the behavior I see for the group admin.
I guess I need to know how to fix, or remove if I can't so hopefully they will just click on the Forum button instead to get back to all the main topics page.