Is the damaged buyer obligated to pay the price of returning the damaged item if that is stipulated, and is his claim of the item's damage accepted without proof?

Selling goods online is permissible under Islamic regulations. The goods are under the seller's guarantee before the buyer or their agent takes possession of them. After possession, they are under the buyer's guarantee. If the goods are damaged before possession, the seller is responsible and must refund the price to the buyer. However, if they are damaged after the buyer takes possession, the seller is not obligated to do anything. In the event that the buyer claims an old defect and the seller denies its occurrence, if the buyer provides evidence or common practice supports their claim, then their word is accepted. Otherwise, the seller's word is accepted, provided they take an oath. If the seller commits to guaranteeing the goods and refunding the price along with the shipping cost, this commitment is valid, and the buyer is not obligated to pay the shipping cost when returning the goods due to damage or defect.