I have been able to duplicate this and thank you for bringing it to our attention.  This unexpected bahavior has been reported to our development and I have attached you to this. You will receive an email when one becomes available. As a workaround you would be able to got to Limitation on Business Interest Expense (8990) screen and in the box that says Current year business interest expense, before the section 163(j) limitation* enter the amount there. This will override the amount on the worksheet.