Are you still maintaining this thing? I had a PHP form that already had name taken. It's not good for syncscroll to use something that is already used by the form.
Around line 51, I change to this:
if (!(name = el.dataset.syncscroll)) {
Other than that it's working great!
By the way, I also changed line 33:
var elems = document.querySelectorAll('[data-syncscroll]');
That way the class does not need to be set.