For those banks that are correspondent lenders on the secondary market, who is in charge of compliance on these loans? Our name is on the docs as the lender and then after approximately three days they are sold. Thanks!

You are.
Treat every loan as if it's not going to be bought by the investor. Make sure everything is the way it should be. You don't want to have to buy back the loan because there's an error the investor doesn't want to live with.

Also, check the contract with your investor. The contract should tell you under what conditions you may have to buy back the loan (compliance errors, etc).

This is an asset quality issue. Look at your promises in the contracts between you and the investors. Your bank represents and warrants each loan you deliver to be free of legal/regulatory defects. Like any other product you sell, there should be sufficient quality controls in place to assure that you deliver no less than the fully compliant paper you offered for sale to the investor.