I have taken a look into your code for the fantastic ui powered by jQuery ui.
When you change the state of a buttonset the viewport jumps to top. I have found a way to prevent this.
jQuery ui moves the input[type=radio] out of the viewport to replace them with buttonsets. When the state of a radio-button changes the viewport tries to scroll to the element.
The solution is to add class="hide-if-js"
to the input-elements type radio.
I hope that is helpfully.
Thanx for your fantastic work
LJ