Usually, the company may request for the defective items to be return for warranty repair.
You will need to follow the warranty claim procedures of each seller. Below is an example of the procedures for your reference.
1) Report to the seller your defective items. Providing documents: Purchase order or Invoice, Part number, serial number and fault of item.
2) Fill up any claim forms. You should receive an Return Authorized (RA) number from the seller for your defective return once they approval your warranty claim.
3) Return the defective item stating the RA. Usually freight will be bear by buyer. As freight is not covered under warranty. Provide the shipping & tracking of the return to seller.
4) When seller received the defective item, they will evaluate, repair & return to you.
5) If the item is beyond repair but under warranty, the seller should replace the item or provide alternative if the model is no long in the market.
6) Do take note that if after evaluation the fault is not covered under warranty terms, you will need to pay for the evaluation. A quotation will be given for your decision to proceed with the repairs.
Cheers!