Problem: Object on Slide Master Changes State Without Trigger

Greetings,

I've created a slide master with several layouts that are subject to it. On the Master is an image that has several states. Each state is supposed to appear based on a numerical variable. The triggers for this numerical variable are placed on buttons throughout the course. The slides on which these buttons reside are built using this same Master slide layout. 

The image state changes correctly once the first button is clicked. Once the learner reaches the next point in the course at which a state change should occur, however, the image reverts back to its "Normal" state--without a trigger telling it to. It remains in the "Normal" state after that point. 

I've looked at my triggers to confirm the logic and have also confirmed that the slides are on the same Master layout with these state changes. I'm stuck--why is my image not changing state when I want it to?

I appreciate any insights y'all can provide. 

Thanks!

Ashley