Thank you for narrowing down the problem. It is indeed the tipping plugin. However, after much testing, my suspicion is that how $cart->additional is handled by the shopping cart, "ungroups" grouped options.
Even just using the code below will already ungroup the options.
defined('_JEXEC') or die('Restricted access');
class plgHikashopTwt_tip extends JPlugin {
function plgHikashopTwt_tip(&$subject, $config){
parent::__construct($subject, $config);
}
function onAfterCartShippingLoad(&$cart) {
$object = new stdClass();
$object->price_value = "100.00";
$object->price_value_with_tax = "100.00";
$object->price_currency_id=2;
$object->name="Tip";
$object->value=0;
$cart->additional['tip']=$object;
}
}
Feel free to use the FTP and Joomla access info to check into it...
Thank you!
PS: Will let the hosting provider know about OVH.