After payments have been created an applied to an outstanding pledge, they are listed on the Installment/Write-off Activity tab for the pledge. Once a payment has been made, it can be adjusted to $0.00 at any time (before or after posting). Users often make this adjustment rather than completely deleting the payment so that there is a viewable history of all transactions. After a pledge payment is adjusted to $0.00, it still appears on the Installment/Write-off Activity tab for the pledge.
However, if the pledge amount is adjusted, this causes the installments to be re-distributed to correspond. This results in the $0.00 payment being removed from the Installments/Write-off Activity tab.
Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch.