Problem using security groups with an app

I am using a security group to control access to an app (permissions).  When I save it and come back to it later it is gone.

When I manually assign someone and come back to it, the person is in the permissions when I come back later.  If I add a security group at that point (with some manual assignments) and come back to it, it has both the person and the security group.

Why does there need to be at least one manual assignment before groups are retained.

I appreciate the comments:

• I am spelling the name of the group correctly, the group has several members
• the group does not remain in the permissions until at least one person is added by their email added as a separate entry
• after that the security group will remain in the permissions