Hi Joe,
Thank you for responding! I've tried a few different things in this project so the project file is a bit of a mess, but if you'll excuse my mess, I will share it here.
The slide with the mysterious layer is slide 1.86 and it's the Knowledge Check Game (Base Layer) where the "Correct Feedback" layer is showing over the top. I continued on with the project which has allowed me to figure out that it is the Q7 Correct layer overlaying the base layer.
I tried to duplicate the layer and show the duplicated layer when the timeline starts, which worked except I have to figure out how to reset all the triggers to function properly. I was just in the process of recreating the entire slide when I received your response.
Attached is my project file, again please excuse my mess, it's a work in progress.
Thank you for any help you can give me!