If you make a partial mortgage payment one week and then pay the rest of the mortgage payment in that same month before the due date then your credit score should not be affected or lowered.
As long as the full mortgage payment is being made before the due date then your credit score should be okay and not be affected badly.
However if you only make a partial mortgage payment in an entire month and then pay the additional portion of the mortgage payment the next month with the full mortgage payment then your credit score could be affected and the bank may report your mortgage payment as late.
If you're gonna only be able to pay partial mortgage payments once in awhile then contact your bank and let them know so that they might not report it to the crediting agency to lower your credit score.
I have had to make partial mortgage payments every once in awhile but I contacted the bank and since I had been on time with the mortgage payments before I had no issue with them working with me and they didn't report the late payments or missed payments as being late.
So my credit score was not affected.