I have found the add/remove quantity buttons don’t work with mix and match products I asked woo and they said:
"My answer on that question (helgatheviking is me!) is still the right direction to take here. jQuery’s change event is only triggered by a manual browser event, so you need to chain a .change() event after the value has been set by whatever “click” script is used by your theme.
You could also try to apply the fixes yourself. You will need to find the source of the plus/minus buttons script. It appears to be here: https://www.faracrevineyard.co.uk/wp-content/themes/sydney-pro-ii/js/main.js (though your site is currently loading the minified version, so you’ll need to fix and then regenerate a minified version).
!isNaN( currentVal ) && $qty.val( isAdd ? ++currentVal : ( currentVal > 0 ? --currentVal : currentVal ) );
might need need to be:
!isNaN( currentVal ) && $qty.val( isAdd ? ++currentVal : ( currentVal > 0 ? --currentVal : currentVal ) ).change();"
I would be grateful if the theme could be made compatible with woo commerce as that is why I paid for it over Sydney…