Zencart v1.5.1

EO 4.1.4

I don't have related plugins in the admin

Display Prices with Tax: true
Display Prices with Tax in Admin: true

The only thing I did notice is that if I comment the following line in functions/edit_orders_functions.php the error doesn't happen anymore, unless I add a product (so if I simply update address or prices it doesn't happen)

PHP Code:
function eo_get_order_by_id($oID) {
    global 
$db$order;

    
// Retrieve the order
    
$order = new order($oID);

    
// Add some required customer information for tax calculation
    // The next method has been modified to add required info to the
    // session and global variables.

    // zen_get_tax_locations();   <============================= THIS COMMENTED