Angular 5 and Material stepper

I’m using Angular 5 and the Material stepper.
I have a Material tab control with multiple tabs, and inside each tab is a stepper with multiple steps.
Everything seems fine in the stepper on my first tab, but when I go to the next tab, the stepper seems to show both steps, rather than just the first step. Its as if both are active.
I don’t believe I’ve coded any differently from what I did in the first tab. Has anyone else seen this behavior and possibly have a solution?

I haven’t used the stepper, but Material is definitely still in need of expanded documentation. Do you have a stackblitz or something that you can link to?