Hi!
I’m not sure if this is possible, the scrollbar script might be capable of it. Scroll propagation by definition is not cancellable programatically, there are tricks to get around it, but usually they get patched up on browser updates.
Anyways, I’ve looked up the script documentation, and there appears to be a way which should work on most browsers. Try putting this custom code to the bottom of the functions.php file in your active theme directory:
This may not work at all, but it’s worth a try. The scrollbar might be a bit different after this code, as it will fully re-create the scrollbar upon displaying the results. Let’s hope it works 🙂