I've posted an almost similar issue on the General Problem forum.
I have a course set to Separate Groups and students must be in a group to access the course.
Each of the Activitiies is als o set the the same.
I have two Non Editing Teachers...renamed Team Leaders in a the group.
I wanted them to only be able to view the gradebook of that Group.
One of the Team Leaders does see only the group Grades with "Separate Groups: Group A at the top.
The other Team Leader can see ALL participants of all groups, even though their view shows Separate Groups: Group A at the top.
When that Team leader clicks the Participant link, they see all participants, but hitting the F5 refresh then chages to that group data only.
Any idea why one Team leader role acts correctly and the other doesn't?