What is the Shariah ruling on an Islamic insurance company paying a late penalty to the buyer, due to the delay in settling the price of the house with the seller?

If the compensation is for delaying the payment of the price, then the seller is not permitted to demand it, because it is explicit usury (riba), and it is Islamically void and forbidden. However, if someone is compelled to pay a fine by positive law, there is no sin upon him for paying it, and the sin is upon whoever forced him to do so. The Islamic Fiqh Council of the Muslim World League has unanimously agreed that a creditor's condition of a financial penalty on a debtor for late payment is the forbidden usury of the pre-Islamic era (riba al-Jahiliyyah). A penalty clause is permissible in financial contracts, except for contracts where the primary obligation is a debt, such as a deferred price, as that is explicit usury.