Possible reasons for ACLs to fail
Craig - I can't comment on why you might have conflicting ACLs, but want to mention the Permissioned Relationships as ACLs which we built and contributed to provide another solution for multi-level permissioning. You can read about it via the link, but it may suit your need and deals easily with the situation of Staff Member Q needing to access the contacts in two regions, but giving Q a relationship with Region A and Region B, and therefore seeing all those contacts that the Region A and B have permission to access.