Blank Page in Quick Order

[rdigital]

Hi, I have a very strange problem, if you access this site (https://bit.ly/2NYi3E4), put a product in the cart, go to the shopping cart, you will see that there are several FEATURED DISCOUNT CUPONS, you can click on top of any one, or paste this here SALE10%OFF for example, so clicking OK will give a white screen, if you give an F5 it will continue normal, only the white screen the first time you will apply the CUPON, already the debug is already enabled in (if (! defined ('_ PS_MODE_DEV_')) define ('_ PS_MODE_DEV_', true);) but still it does not generate any errors, so vi is a problem in the override / controllers / front / OrderOpcController. php, because if retreat it goes normal, it's a FKCustommer file, does anyone have any idea how to debug this error? ...... remembering, _PS_MODE_DEV_ is already active.