I have a rig in Slot 1 and Slot 2 and another in Slot 5.
If I press the button (right) to jump from Rig 1 to Rig 2 (Slot 1 to 2) there is no problem.
If I press the buttom again, the black background jumps to Slot 1 (Rig 1) back.
It does not jump to Slot 3. It's not possible to jump to Slot 3, 4 and 5.
Attached is a video in a .zip file which shows the bug.