Arch Disappears When a Certain Swatch Is Selected

Hi folks, odd problem here. I have an arch that was modified from an original game arch to start. Whenever I select the first swatch to place the arch however, it doesn't show on the wall. If I select a different swatch, it does show. Another odd thing, if I place the arch with another swatch selected, that first swatch disappears if I attempt to select a different color. Examples below:

Any ideas? Here's the file if you'd like to take a look. Thanks!