Is the buyer obligated to pay the owner of the machine after the latter returned his money and the machine remained in the buyer's possession and he repaired it at a low cost?

The seller's refund of the machine's price to the buyer due to a defect is considered a فسخ (annulment) of the contract, making the machine the property of the seller once again. The buyer is not permitted to dispose of it except with the seller's permission. Scholars have differed on whether the buyer's possession of the sold item after annulment due to a defect is considered a trust ( يد أمانة ) or a guarantee ( يد ضمان ). The effect of this disagreement becomes apparent if the machine is damaged without any transgression on the part of the buyer. The point is that the buyer does not own the machine after the price has been refunded, and it must be returned to the seller. They can also mutually agree to deduct the repair cost from the price.