Mortgage Account (unlinked) Principal Curtailment payments affecting next payment due date

I am using Quicken Deluxe 2019 for Windows - I have my Mortgage from my Credit Union set up in Quicken. This year I started making additional (unscheduled) Principal Only (Principle Curtailment) payments. This should not effect my regular monthly payment date or amount (except that Quicken should recalculate the portion of each payment that is interest and principal). The problem is after making about 5 additional payments of $1000.00 where my monthly payment is $1477.00, I now do not get my monthly reminder to enter this transaction and when going to the Mortgage Account in Quicken, it currently shows I do not owe this regular payment until Feb 2020 (it is currently time for the Sept 2019 payment). How do I correctly enter these principal only payments so that it does not effect when Quicken thinks my next regular payment is due.