Background animation forces landing page off-centre on refreshing, how do I fix it? (HTML/CSS)

I’m still pretty new to all this; the problem is that I have a background animation that zooms in on the background (the “breathe” effect) and when I refresh the page, the starting position for the page is off-set to the left by how much the background has moved ( in relation to the initial/correct position). I have a jsfiddle made, that can show the action of the background/the effect but not the problem; I don’t know how to refresh the jsfiddle rather than re-run it fully