Scheduled Transaction

I had a scheduled transaction for my house payment. I just looked at the history and for some reason about 6 months ago it stopped using the loan data to calculate the amount of principle and interest. Every month the principle and interest payments have not changed, throwing the balance off. Instead of the principle amount going up every month and the interest amount going down every month, these amounts have remained constant. How can I get Quicken to use the correct split info? Is a scheduled transaction the best way to do this? Thanks, Jimt