.scrollTo does vertical but not horizontal sometimes

[awlayton]

This happens very infrequently when I run the Travis tests. For example:

horseman
    .open('http://www.google.com')
    .scrollTo(50, 40)
    .evaluate(function() {
        return {
            top: document.body.scrollTop,
            left: document.body.scrollLeft
        };
    })
    .log() // *Sometimes* outputs {top: 50, left: 0} instead of {top: 50, left: 40}

I am not sure how horseman could cause this, it might be node-phantom-simple or PhantomJS. Either way, I should try to figure out what is happening.