Bounding Box of Image Within Slide Kills Button in Slide Master

This is re-create-able.

1. Slide Master - Create a button, say the lower right-hand corner of the prez window. Make it jump to next slide, or whatever, doesn't really matter.
2. In a slide in a scene, add a graphic whose bounding box covers all or part of the button in the slide master.
3. Run it.

For me, the mouse apparently could never "see" the button for the bounding box.  And because of the color of the background image in the slide master, I couldn't see it. A really good test is to make the image's bounding box only halfway cover the button. Then run it. The button is active when the cursor is outside the bounding box. Once it goes inside, the button deactivates.

This little gem cost me about an hour, including hair-pulling time. But, using the scientific method, and some choice words, I figured it out. I hope to goodness it isn't just me. Somebody want to try it? I've added a sample file so you can see.