For 2017 filings, the property was "sold" or distributed or otherwise disposed of to that shareholder. The shareholder, now a private person who might or might not be running a business with it, then has the assets and accepted the responsibility to assume the debt. As personal debt, there is no "business interest on the personal tax return." Example: A construction site trailer now is used for a hunting camp. Or, the person has a "new" business and this is part of the Business tax return, such as Sched C or 1065 or a different S Corp.

Perhaps 2017 was not filed properly?