Res judicata issue for claiming the rest of unclaimed debt with a new case

I gave a loan of AED 200,000 to a person. He gave me a letter acknowledging that he received 200,000 from me.

Later on, he gave me cheques for 100,000 and a letter stating that this was partial payment of a loan. The cheques bounced.

I made a court case and submitted the cheques and acknowledgment of partial payment.

I did not submit the letter acknowledging that the debtor received AED 200,000 from me.

I won a verdict for the 100,000 AED.

Later on, I started a court case for the remainder of AED 100,000. I submitted the letter acknowledging that the debtor received AED 200,000 from me.

I explained that I had already won the case for the first 100,000 and this was a lawsuit for the remainder of 100,000. I won the First Instance and the Appeal judgment.

Suddenly, the case was rejected by the Cassation Court. They wrote that my case for the second payment of AED 100,000 was a repeat of the first case of AED 100,000 and had already been judged

What can I do in such a circumstance?