Possible $10k Deal with Roadblocks- NEED ADVISE

[Spencer I.]

I have a great wholesale deal under contract for 45k.
ARV100k
Repairs 5k-10k cosmetic only
Price 55k

I have at least 5 investors with cash ready to go BUT, the previous owner claims the house was never paid off and placed a lein on it for 70k (owner financed back in 1998). But the house is in the sellers name (taxes and deed), and the sellers claim the house was paid off. I actually spoke with the previous owner who says the sellers deceased father filed bankruptcy 3 times and never paid it off plus interest hoa fees and back taxes. So he wants 70k to release the lein, but will not furnish any paperwork at all. I think it's possible the sellers did pay it off.
What would you o to make sure you don't loose the deal if there is still a deal there?

All opinions welcome.