Limitation of Application of Customer Payment of 10000 Invoices

This is due to the limitation of the page on Payment, in Edit mode, that can show only 10000 records.

 

If customer has over 10000 invoices, the invoices cannot be all displayed. The original Applied Amount gets changed.

 

The workaround would be to change the Dates on the header to a smaller range to reduce the number of invoices to display. It defaults to All so it shows all the invoices. The fields are also sticky so the same date range applies when you try to edit a different Payment Record.