Widget moves a little bit to the right while scrolling

Hi,

First of all, thanks for a really wonderful plugin!

It overally works great, but there is a slight problem with my layout.

While scrolling on my site ( http://kulturawplot.pl ) the widget moves a few pixels to the right, covering part of the content area (and Disqus comments). Do you know what may be the reason?

Thanks again and keep up the good work!

KWP

https://wordpress.org/plugins/q2w3-fixed-widget/