Change to mortgage P&I caused by extra payment

[JimR]

Longtime GNUCash user, I could not get my mortgage principal and 
interest from the "Mortgage and Loan Repayment" to match exactly what my 
bank was reporting.

Earlier this year, I refinanced my mortgage with the same bank. This 
amounted to paying out the old mortgage, and creating a brand new one.  
I was thrilled that for months, it was matching to the penny.  Then I 
went to the bank and made an additional payment directly against the 
outstanding principal.  After that, the GNUCash M&LR figures no longer 
match.  It seems that this extra principal payment has the effect of 
adjusting my monthly payments so that more of each subsequent months' 
payment goes against the outstanding principal and less against the 
interest.

However, my "Mortgage and Loan Repayment" in GNUcash does not recognize 
this.  What is the correct process to make this work? Do I have to 
delete the saved template in the M&LR template, and enter a new one with 
the adjusted outstanding principal?  I try to make these extra payments 
once a year, so that would be a bit of a pain.

Suggestions?

-- 
JimR