The settlement baked into the Residential Capital bankruptcy agreement is facing new challenges, including one from Warren Buffet’s Berkshire Hathaway and another from unsecured creditors. When ResCap announced its bankruptcy last month, it did so with a plan to sell its mortgage origination platform and servicing rights to Nationstar Mortgage, a division of Fortress Investment Group, for $4 billion and its portfolio loans to its parent company Ally Financial. Part of the deal is a release of legal liability for Ally, which will pass along some of its lingering obligations – like follow through on the...