I see what the issue is on your site. When I scroll to the bottom the vertical scroll jumps up and down and the page number in the URL bar jumps between 2 and 5.
However, I am unable to reproduce this issue on our development site.
Also, it only happens in Chrome for me. It does not do it in Firefox.
I may have recommended this to you previously but have you tried disabling ALL plugins, except the required ones to see if the issue persists?
You should disable them all and then log out. Clear your browser cache and cookies and see if the problem persists.
You can also create a website backup before just in case.
You have many plugins installed and running, there is a big chance one of them is causing a conflict.
If you do that we can try and identify which one is causing the issue.
Unfortunately for now that is all I can recommend as there are no JS or CSS issues popping up on the site and it only seems to happen with Chrome.