Image in the bg moves outside the container

[bovas85]

Expected Behavior

The image covers the entire div always when scrolling up or down

Actual Behavior

You can see behind the image once you scroll enough on the default speedFactor

you can check http://antilophia-vue.nakedtesting.com/chile/ for a live example (scroll down until you only see like the screenshot above.
The image will transform too far down and cause the background to be visible

Environment

• OS: OS High Sierra, Chrome latest, Firefox latest
• NPM version: latest
• vue.js version: latest
• vue-parallax version: latest