Magento 1.9 : Product list page wrong sorting by price

When we install webtex_customergroupprice it has a bug when it sorts products on product list page it is not correct. For this we need to change collections orderby.

We add

$collection->getSelect()->reset(Zend_Db_Select::ORDER)->order('(min_price)'.$orderDir);

at the end of the function public function sortByPrice() in file

app/code/local/Webtex/CustomerGroupsPrice/Model/Observer.php

Refresh Cache and the sorting is perfect.