Notice the width of the sidebar to begin with and then scroll down a bit. If you look closely, you will see the sidebar getting wider.

Anyone seen this before? – and do you know how to fix it?

Thanks!

We have checked,

@media only screen and (min-width: 640px) {
	section#sidebar > div#bag_list_widget {
	   max-width: 320px!important;
	}
}

Use this css in your file, you will get rid of this.

Thanks,