Debuging OG access field I have few roles in OG groups: Visitor, Reviewer, Member, ...

Visitor and Reviewer are added roles with (at the moment) exactly the same settings. Unfortunately somehow Visitor is inheriting Member's access rights while Reviewer is not. 

I checked everything and all looks fine. I tried hacking OG code (I switched off the default role inheritance), checked og_role_permission table and all looks fine. But still whenever I give some rights to the Member role, Visitor user is somehow inheriting them while Reviewer is not.

My website is making use of OG roles everywhere. I have context, rules, custom code depending on it. And while everything works fine, field_access is behaving strange.

Do you guys have any idea how can I go on with debugging this issue? Is there a place in node_access module where I could put some debug code informing me what is going on?

UPDATE

I switched off all the custom code, changed drupal core to older version, made sure that access settings for Visitor OG role are exactly the same as Reviewer's. 

I rebuilded cache, rebuilded access rights, changed browsers, went through code in OG and data stored in the db.

Still users with Visitor OG-role inherit rights from Member OG-role, while Reviewer does not. This bug is killing me.
Unfortunately I have to surrender. There is a bug somewhere in the og module but I can not track it down. What happens is that the default group membership role can not be changed. Changing the definition of OG_AUTHENTICATED_ROLE in the og.module does nothing. Because of that all the access rights given to the "member" role are being inherited by all the other roles and so they can not be weaker.

My solution will have to be creation of new members role - "full_member" where I will be able to define roles of that member. I will also remove all permissions from the "member" role. The problem is that I will have to redo all the rules, contexts, pages, blocks, custom code and so on. Few days of boring work and debugging.