Breaks when combined with OG

My site has OG7 on it with private groups and is working fine - when anon users try to get to a private post on a private group eg
http://venturacottage.homedns.org/d7og4/content/gov-meeting-2 - they rightly get access denied
but when I put on Content Access
http://venturacottage.homedns.org/d7og5/content/gov-meeting-2 - the content shows up
I DO need your excellent module as I have a content type assignment from pupil that exists within each og school class but at
admin/structure/types/manage/assignment-from-pupil/access > view any content is unticked for everyone but the teacher role.
View own content > student is ticked thus when a student logs on they can see all content in their own class group but cant see billy smilths homework!
But combining OG and Content Access seems to break.

I am aware of
admin/structure/types/manage/article/access
admin/structure/types/manage/group/access
> advanced > Give content node grants priority and have tried various settings inc -10 - no luck. I can give you access to the demo sites if it helps.