Mortgage payments are recorded in cycles.
For example:

Mortgage payments are, normally, due on the first of the month and becomes late on the 15th.

Tony submits a mortgage payment of $950.00 on April 18th and another payment in the amount of $950.00 on June 1st. However, the June 1st payment is returned back to Tony and foreclosure or acceleration of foreclosure begins.

Technically, Tony is out of the payment cycle and without a repayment agreement, the April and June payment will not be applied, unless Tony pays April, May and June payments, he will be considered 90 days delinquent.

“By the way, it is not uncommon for the April payment to set in suspense at his mortgage company and never applied.”