I know this is an old post, but this worked like a charm.
Safari seems to have some differences in the way that it handles the scrollposition's values (given the way the viewport is calculated), causing the autokill: true to be forcibly called. I just set it to off for safari and now it works fine.
I also want to mention a fix for a similar problem i had a month ago, and it's related to the metadata tags of the website.
Certain gsap scrollTo features seem to break unexpectedly on Safari ( in my experience, using any of the features that use translate() ), but another forum member had written something along the lines of needing some specific metadata tags in your html head.
<meta name="viewport" content="width=device-width, height=device-height, initial-scale=1, minimum-scale=1, maximum-scale=1, user-scalable=no">
Thanks again for the fix.