discard duplicate http request with nginx ?

Hello
I have been using nginx for a year now and without a doubt it has been very useful as a proxy server for distributing my static content.
now , I have a problem with an application which is sending the same http request POST twice to another application causing an error , it is obviously a bug that need fixing , but I was wondering if, while the bug is being fixed , if i can use nginx to drop the second http request , this particular http request should never be the same payload at any time so there is no need to put a time restrain on it .
Any suggestion would be a great help

Regards

Luc