Out wrapper get height of inner wrapper when affixed

[StudioVDS]

Hi, I'm trying to get your Sticky Sidebar implemented in my website. On one page it is working perfectly! On another one it isn't. When the sidebar is getting its fixed state the main content is jumping down.

Looking in at the code I see that the sidebar os not getting the height:0px inline styling (the sidebar on the other page does) but it is getting the height of the sidebar when it is not fixed something around 400ox height. So the content is jumping down this 400px. Why is this and how can I solve this?