Does paying a down payment to the seller before signing the تنازل (waiver/relinquishment) and إحالة (referral/assignment) document to the bank make the Murabaha transaction for purchasing an apartment impermissible?

The aforementioned transaction is impermissible due to the possibility of prior collusion between the buyer and the apartment owner. It is not permissible for the bank to enter into a murabahah transaction if collusion is evident. Any prior contractual agreement between the commissioning client and the original seller must be cancelled. Furthermore, signing a document of waiver of the earnest money and assignment to the bank makes the amount a loan from the client to the bank, which falls under the prohibition of combining a loan and a sale.