Product: Credit reporting, credit repair services, or other personal consumer reports

My wife and I took out an car lease with Chrysler Capital in XX/XX/XXXX. The car lease was over 36 months at a monthly cost of approx {$450.00}. 
We signed up for Autopay and the first 35 payments were all paid in full and on time using this process. We received a number of calls from Chrysler Capital in the final month, informing us that we had excellent credit and because of our excellent payment history they offered a number of incentives to enter into a new lease. We decided not to do this as we did not want another vehicle from Chrysler. 
Ahead of the 36th and final payment ( which was due on XX/XX/XXXX ), and for reasons unknown to us, the Autopay was cancelled. 
As there was equity in the vehicle, we decided that we would sell the vehicle to a dealer and keep the remaining equity for ourselves. We requested a settlement figure from Chrysler Capital - this was provided to us on XX/XX/XXXX and expressed that the settlement figure ( of approximately {$20000.00} ) " was good through XX/XX/XXXX ''. The settlement figure included the final monthly payment of {$450.00}. 
Between XX/XX/XXXX and XX/XX/XXXX, we attempted to sell the vehicle to two different Chrysler dealers, but after some time were then advised that it was not possible to sell the vehicle to a dealer in the final month of the lease. 
As a result, we had to purchase the vehicle ourselves and we requested another settlement figure from Chrysler by phone on XX/XX/XXXX. I attempted to pay the amount due over the phone by card ( including the final monthly payment ). I was advised by the customer service agent that it was not possible to make the payment by phone and I would need to mail them a check. 
I expressed concern to the agent that this would result in me becoming delinquent with my payment - both the XX/XX/XXXX deadline from the settlement figure and with the final payment becoming 30 days past due on XX/XX/XXXX. The agent told me that I had no reason for concern and that as long as the check was mailed in the coming days then there would be no problems. 
Nonetheless I sent the check for approx. {$20000.00} that afternoon ( XX/XX/XXXX ) by overnight service from XXXX. 
We received the title documents from Chrysler Capital a couple of weeks afterwards and confirmation that the account was closed and satisfied in full and we thought nothing more of the incident. 
We are now applying for a mortgage and discovered in XX/XX/XXXX that our credit score has fallen by approx. XXXX points each as a result of Chrysler Capital declaring that we were 30 days late on the final payment of the lease ( and reporting it to all 3 bureau ). According to records from our online account, Chrysler Capital applied our check to the account on XX/XX/XXXX, some 6 days after it would have been received at their offices. 
We have contacted Chrysler Capital through their dispute resolution process and they stated that they had found no reason to change their reporting. They did not confirm they had listened to the call recording from XX/XX/XXXX. 
We have otherwise a perfect credit record and have always made all of our payments in full and on time.