This is typical of dabs and some other online retailers - place an order and it's dealt with and delivered in exemplary fashion. But if things go wrong.....
You should not have to pay for any item to be returned if it is faulty.
Your best bet is to contact the manufacturer direct - most are very keen to maintain good customer relations and will pull out all the stops to help you.
Normally the faulty goods will be collected and replaced without further ado or cost to yourself.
It also lets manufacturers know which retailers are creating a bad image with regard to their product sales and that can only be good in the long run if the right steps are put in place.