My tax liability went up about $300 when I added a 2nd 1098 (Mort Interest Statement). It seemed that the end of 2018 mortgage balance is what triggered the increased liability.
If anything, additional paid mortgage interest should never increase liability, right?
The amount of mortgage interest is now capped based on mortgage principal amounts of $750K and greater. The link below will explain in detail the changes as a result of the recent tax reform.