Base layer disappears when navigating in lightbox

Hi everyone,
we recently added an overview in our project to give users the opportunity to go back within the training and revisit topics of their chosing.
Our overview is displayed as a lightbox that opens from an icon placed on the master slides. In that lightbox the user can choose a slide that he wants to revisit. That slide will then open within the lightbox although we used the trigger "go to this slide". This is not what we originally intended, but we could live with it. But it might be part of the problem. 
The actual problem is this. If the user chooses to display the slide they were already on, when opening the overview, meaning the slide that you still see behind the lightbox, this slide disappears in the back. If they now close the lightbox, there is only a blank page with no possibilities for navigation left.
Do you have any ideas how to prevent this, that would be great!

I think it might help if we could open the chosen slide outside of the lightbox, but I couldn't find a better trigger to make that happen.
I hope I was able to describe the problem well. Every hint is really appreciated. Thank you!