I was also having the same problem where my mortgage interest was going to 0 on Sch A. I followed all the steps mentioned (delete and restart) a couple of times, the last time when the refund jumped back up, instead of hitting the continue button, I clicked on the review my return at the top of the screen and the Sch A kept the interest at almost the exact amount that I calculated manually. There is in my opinion a bug / miscalculation in the Home Premier version I am using
