What is the ruling on a seller who concealed a defect in an item purchased by a buyer, and the buyer returned it within the legal option period, but the seller evaded returning the money?

Since you have become aware of many defects that the seller did not disclose, there is no blame upon you for retracting the purchase and demanding the price, and the seller is obliged to return it. This is because the option of defect is established for the buyer. Ibn Qudamah said: "Whenever the buyer discovers a defect in the sold item that he was not aware of, he has the option between keeping it or rescinding the sale, whether the seller knew and concealed it or did not know. We do not know of any disagreement among the people of knowledge regarding this." Ibn al-Mundhir said: "The people of knowledge are in agreement that whoever buys an item and finds a defect in it that was present with the seller and the buyer was not aware of, he has the right to return it." The seller must fear Allah and return the price without procrastination.