Aah the issue is this CSS:
.woovr-active .variations_form .variations, .woovr-variations + .variations {
display: none;
}
The Javascript scrolls to the top of the default variations
table element. Which is being hidden by that CSS – which is breaking the scrolling.
I am not sure if you’re in control of that CSS or its the variations plugin being used. Worst case you can overwrite that CSS with this:
.woovr-active .variations_form .variations, .woovr-variations + .variations {
display: block !important;
overflow: hidden;
visibility: hidden;
height: 0;
margin-bottom: 0 !important;
}