Disable sticky menu

Hi,
Can you help me to disable the sticky menu bar? I need to disable it because I guess it is the reason why whenever I try to scroll to the bottom of the page, the page would bounce up. It happens only when I resize the page to a certain size as in the clip here. https://www.youtube.com/watch?v=GIV–Nx0yFM&feature=youtu.be

Here is my website : http://demo.scscenter.org/
Thank you .