After some investigation we found the problem, we tried all your steps and still no luck.
However the problem in question was due to the “Nice Scroll” Part of Avada, We turned off, Avada -> Theme Options -> Advanced -> Theme Features -> Smooth Scrolling
“Turn on to enable smooth scrolling. This will replace default browser scrollbar with a dark scrollbar.”
This is where the problem persisted from, our client very much likes this scrollbar and it would be nice to see it fixed!
I hope my insight from this issue can help resolve this for other people who have the same issue.