Issues with making a "Skip ahead if passed" quiz optional

I'd like to use the "skip ahead if passed" feature to create a test-out quiz. However, I want to make the test-out optional; if a user doesn't want to attempt it they should be able to skip it and just take the course.

I tried achieving this by putting a button stack before the quiz. One button goes to the quiz, and the other button goes to the lesson after the quiz.

Unfortunately this seems problematic, because if you skip the quiz, you can advance using continue buttons, but if you navigate backwards at all, the continue buttons are gone (which is normal behavior) but the navigation is still locked.

In other words, once you've activated a "skip ahead if passed" quiz, the quiz is the ONLY way to unlock subsequent content.

This results in the user getting stuck, and not being able to proceed without going back to the quiz and passing it.

Is there some workaround for this? Has anyone else tried making a "skip ahead" quiz optional?