What causes scrolling lag on mobile devices?

Question

JavaScript

The project is on the NDA, so I can’t show anything.
But there are not many scripts, the site is quite simple.
Tested on an iPad mini and a newly purchased iPhone SE. So there can be no problems with mobile phones.
One script is hung on onscroll - checking scrollTop via jQuery. onscroll hangs not on window, but on div.
It lags both the scroll of this div and the native scroll of the window.
There is nothing more to do with scrolling.
There is also SVG weighing 150-200KB (there are a lot of them, but only one is shown on the page) - a lot of details, a veil of text in 228 lines, each of which contains several screens of text.
Could it be the reason?
PS: at the moment, all 13 huge SVGs are included as a sprite on the page - can this affect? The page as a result weighs more than 2MB (still thinking about solving this problem)

Answer 1

I think that you can check what's the matter by excluding elements. Eliminate blocks and test.