I've noticed the same issue of negative amount for "Adjustment of Interest and Points Reported on Form 1098" on screen "California Mortgage and Home Equity Interest".
I also have 2 mortgages (2 properties, 2 loans) and one of my loan has been transferred from one lender to another lender sometime in the middle of the year. When I entered the beginning and ending loan balance, I entered "0" for the loan which is transferred to another lender as at the end of the year, the loan balance from that lender is 0. This made the negative number go away and changed to 0 value. I hope this is helpful and is a solution for you too.
