A Curious Issue with Trigger and Conditions

Hello everyone! I ran into an issue with a trigger and its conditions, which I eventually resolved but am curious to learn more here: 

In my project, I have this menu slide with three icons which, when the user clicks on, will "jump to" the corresponding slides. I also have a continue button whose initial state is disabled. The trigger set-up is: Change the state of the continue button to "normal" when the "timeline starts on this slide," if the state of each icon is "selected."  

After receiving feedback from some friends, I decided to "lightbox" the corresponding slides, rather than have Articulate Storyline "jump to them. The weird thing is the trigger no longer works, even though everything is written the same (Change the state of the continue button to "normal" when the "timeline starts on this slide," if the state of each icon is "selected). The only thing that changed is I lightbox rather than jump to the corresponding slide.

I eventually resolved this issue by dropping the conditions: Change the state of the continue button to "normal" when all of the icons (ovals 1-3) are "selected." (See the image below)

I am just curious to know why the conditions stop working after I began using "lightbox." Logically speaking, I can't tell what was going wrong because the conditions were about the selected states of the icons. Or is there something messed up with "when the timeline starts"? 

Have you encountered this issue before? How did you eventually resolve it? Thank you very much for your time!!