Buying 2nd position debt and challenging a flawed 1st mortgage

[Josh Caldwell]

Challenging a flawed mortgage 

I have read a few stories about home owners challenging flawed mortgages, and getting 1st position bank notes extinguished. 

As I understand the concept (shaky grasp at best) the key is to find a flaw in the record keeping or the filing process as a mortgage is bundled and sold from one bank to another. 

Is anyone out there buying 2nd of lower position debt and then contesting the validity of the senior loans?

If so, how are you doing it, and what flaws are you looking for in the 1st position mortgage. 

Thanks for any help

Josh