Bug? Unexpected motion

Hello

I'm getting a very strange behaviour with a Basic Motion study. I have a study with 2 parts with no mates, no motor, no gravity, and set solid contacts. As soon as the study begins, the parts fly off the screen. How come the parts move even when there's no external force exerted on them?

Here's a video: Parts flying off - YouTube

Thanks

John

SolidworksMotion Studies