Wrong behaviour of "Move all" arrow button on "Change groups for branch permissions" window

1. Go to Forum Structure, choose any branch, press Permissions, press any "Edit" button
2. Press "Move all" arrow button (>>)
As a result, all groups are moved to "Already added" section, but "Registered users" duplicates: one moves to "Already added", other stays on "Available" section
3. Press "Move all" arrow button of other direction (<<)
As a result, all groups are moved to "Available" section, but "Registered users" keep staying on both "Already added" and "Available" section
4. Press "Move all" arrow button (>>)
As a result, one "Registered users" keep staying on "Available" section and TWO "Registered users" appear on "Already added" section (please, see video attached)
5. Press "Save"
As a result, 2 "Registered groups" together are listed in "Allowed" or "Resricted" row