Sticky Sidebar is not Working Properly in Mobile

hello Team,

Sticy Sidebar on http://travel.physcode.com/tours/discover-singapore/ page is not working properly.

when you open this page in mobile or just resize window of your browser, Book the Tour Form and related tours appear center of the screen, so user wont be able to read content of the tour.
please see:
http://flyhighholiday.in/error-sticky-sidebar.png

Thanks