Exception "Transaction Already Handled"

We have recently started getting a small number of members who are getting their rebill attempt charged successfully in Payeezy but are not getting credit for it in aMember. Looking at the invoice log, the invoices that get charged on Payeezy but don't get credit for it in aMember get an "exception" entry in the log, whereas everyone else just has an outgoing request and then a response. When we look at people with the exception code, it shows that they did get an acceptance and as far as we can tell, the return message looks exactly the same as those who do not get an exception. Here is an example of the first few lines of the exception entry:

<invoice-log-item type="exception">
<type>Am_Exception_Paysystem_TransactionAlreadyHandled</type>
<message>Transaction payeezy-js-H22676 is already handled (2)</message>

Server info:
aMember 5.6.0
Zend Framework 1.12.4
PHP 7.3.1-1+0~20190113101756.25+stretch~1.gbp15aaa9 (fpm-fcgi)
OS Linux raiders 4.9.0-8-amd64 ...
MySQL 10.1.37-MariaDB-0+deb9u1

Using First Data's Payeezy interface for our processing.

Anyone have a similar experience?