Well, I made an adjustment so the scrollbar stops going above the header - but I'm telling you guys, based on the changes I had to make in order to adjust this, there is NO WAY this started happening recently. This has been like this, ever since we moved to the "responsive" layout. I just don't think that many people actually use scrollbars anymore, so who would actually notice???
...of course, once it's pointed out by somebody - you can't take your eyes off of it.
Scrollbar > scrollwheel on 50ppp