Mortgage amortization no longer working properly

Quicken has been properly amortizing our mortgage payments since 2012. 
After I entered this month's payment from the Bill and Income Reminders 
window as I always do, I switched to the mortgage account register to 
verify the current mortgage balance. I saw that, not only had the 
balance not changed since last month, there was no payment transaction 
for this month shown in the mortgage account register. I switched back 
to our checking account register and opened the split transaction window 
for the payment transaction I had just entered. The split transaction 
window listed the mortgage principal and the interest expense 
categories, but the entire payment was allocated to a blank line with no 
assigned category. All the loan details in the mortgage account look OK; 
the monthly payment is shown properly allocated between principal and 
interest, but it doesn't get entered that way. The next scheduled 
transaction shows the same thing—a split transaction showing the 
mortgage principal and interest expense categories, but the entire 
payment is being allocated to a blank line with no assigned category.

It looks to me that my problem is very likely related to one of the 
Quicken updates done between December 13 and January 12 since I had no 
issue when I entered my December 12 mortgage payment. I'm currently 
running version R46.12, build 27.1.46.12 under 64-bit Windows 10 Pro. 
I've been on the Quicken subscription model for the past 4 years and 
install any Quicken updates whenever they are offered to me.

I suspect an issue with a Quicken update because I restored various 
(about 6 or 7) Quicken backups earlier today stretching all the way back 
to January 2022 (last year). In every one of those restored files, the 
bill reminder in the Bill and Income Reminders list did NOT allocate any 
amounts to either mortgage principal or interest expense but instead 
entered the entire payment amount to a blank line in the split 
transaction with NO category. All prior mortgage payments going back 
over 10 years were allocated properly by Quicken.

Any help would be greatly appreciated.