OG Access Failing With Entity Reference & Views?

My View fails to display rows (where the entity has no children) to anyone except the superuser. It appears possibly related to a permissions problem with the Organic Groups Access module.

The View should have two columns, Parent Title and Child Count. When I add the reverse Entity Reference Relationship only the superuser can see rows for entities with no children. The View behaves, for non superusers, as if I had checked "Require this relationship" - but it isn't checked.

Here is an example to hopefully make it clearer.

Given this data (child holds Entity Reference to parent - 1:n):
ParentA
----Child1
----Child2
ParentB
----Child3
ParentC

I am aiming for:
Parent | Num Children
ParentA| 2
ParentB| 1
ParentC| 0

After adding the reverse Entity Relationship (before any aggregation) the superuser sees:
ParentA
ParentA
ParentB
ParentC

However, everyone else sees:
ParentA
ParentA
ParentB

Permissions
A user granted the "Node - Bypass content access control" permission will see all rows as expected, the same as the superuser. But no other permission settings resolves the problem. I have been rebuilding permissions and clearing the cache.

Organic Groups
I have private Organic Groups. No groups share data and all relevant nodes are viewable themselves to group members. If I uninstall the OG Access Control module the problem is resolved. However, with this module installed no OG permission settings resolves the problem (I have tried granting all permissions and unchecking "Strict node access permissions").

This appears to be a problem with private OG permissions when using a reverse Entity Reference in Views. However, I can find no settings combination to resolve this. Can anyone suggest how I might progress from here? I really have no idea what to do next.

Thanks, Polly

Update
I have found this unresolved "node_access breaks any query that has node table appearing twice with a left join" issue. Is it the same as my problem. I am fairly new to Drupal so do not understand what this means. Is this likely to get fixed in D7 or do I need to find a workaround?