What is the ruling if someone enters into such an invalid settlement believing the concession was obligatory due to the initial claim?

Primary text

If the transaction is performed as a settlement under the mistaken belief that the concession was obligatory due to the nature of the claim, the person making the concession has the right to claim back the rent for the time the property was occupied and the rent for any other part of the house held by the other party. This is because the property was taken under a void contract, analogous to a sale concluded under a void contract or tenancy under a void lease.