Indeed. For any reason, your "Referrals" group contains only two groups (Ortho and Phys Med), but opens the cardiology group.
Its own action should be: Open Touch Bar Group: Referrals
And you have to add one more group, with the action Open Touch Bar Group: Cardiology.
In order to go back, you have to add another button inside the group, that opens the previous group. There is no "open last group" possibility (maybe @Andreas_Hegenberg could think about this feature for a future update ? 
), but you can emulate it by adding a button that opens the Cardiology group again (or maybe even one that brings up the Referrals group too). As a suggestion, I would make the buttons with the doctors stick to the left, and the "go back" ones to the right - or to the very left, up to you.
I'm a med student on summer vacation, if you need any help let me know!