Recent update showing old data

Hi I have recently updated Manager to 18.1.88. I have found many errors with old data going back as far as 2015.
Sales invoices being overdue or over paid and the same with purchase invoices. I Have fixed a few by making payments / credits etc relating to those dates, but not sure if this was the right thing to do. I did do a back up before updating

Yes, there has been a change in process - read this release [17.9.28] Improvements to automatic credit allocations

The simplest correction is to go to those receipts / payments showing overpaid and make then unallocated to any invoice, remove any invoice selection. These amounts will then flow to those overdue. It suggested that you start at the oldest first and work through to the present.