Is the transaction offered by a participatory bank, in which its profit margin increases with the extended duration of house installment payments, yet without an increase in this margin in case of delayed payment, considered a valid Murabaha from a Sharia perspective?

It is permissible to purchase a house through a bank using the Murabaha to the one who commands the purchase system, if the following conditions are met: that the bank buys the house for itself and takes possession of it, then sells it to you after owning and possessing it, and that the the contract is free from any forbidden conditions. There is no harm in the bank taking a profit margin proportionate to the installment period, for time has a share in the price. This is a permissible sale, and Allah Almighty has said: (And Allah has permitted trade and forbidden interest).