scrolling problem from header image

I can use the main pager on mobiles, but unfortunately swipe scroll down the page is not working on the header. Can you see a reason why this is? This is the site: http://deftcad.driveby2018.co.uk I can send access credentials. Is this support forum private? This is a live wordpress multisite network so changes need to be done carefully to not impact live sites. email: jack@drivebywebsites.com