Left content and Right sidebar scrolling separately, in the Middle section

First of all thank you for this great theme! There’s a difficulty i’m trying to overcome for some days:
When scrolling down (or up) with the mouse, in the ‘Middle section’ of my site, it seems like the left content and the right sidebar are moving in a different pace and separately, instead of scrolling together as one piece. It looks like this is caused by the different height the 2 elements have.
Is there a way to make the 2 elements scroll down together as one piece? (with just a blank space beneath the shorter element, while the longer is still scrolling)

For example, currently when the side bar is much longer then the content, the content stops scrolling almost instantly but remains on screen, while the sidebar keeps scrolling until its end. Only when there is no more sidebar content, the 2 elements scroll down together. This makes the website look a bit unorganized/buggy.

A million thanks! Any suggestion would be greatly appreciated