Safari - Webpage scrolling issue
I am a web developer and I have run into a really weird issue with a client site. When I view the site on windows desktop it operates correctly but the client on a mac is telling me that on some pages, after they have scrolled to the bottom of the webpage, that when they scroll back up to the top of the webpage they are not able to get back to the complete top of the page and instead it stops them from scrolling anymore when they are 100-200 pixels from the actual top of the page so it is cutting off the top of the page content when they try to get back to the top. I do not have a desktop mac but I tried some online mac with safari emulators and I still can't see the problem, but the client has several people on macs that have this problem. The webpage loads just fine but after visiting the bottom and coming back to the top it won't go to the full top of the page. I have never had this issue with a website before and I am wondering if anyone can duplicate this problem on their mac and also if anyone has any idea what is causing it and how to fix it.
Here is a webpage on the site that the client says has this problem:
MacBook Pro with Retina display, macOS High Sierra (10.13), 15" MacBook pro 2017, safari 11.0.1