VERIFIED SOLUTION i
When printing the last page printed is in Landscape, not Portrait like the rest of the document. This seems to force the creation of a dedicated sheet for this page, which ends up on the front of a sheet of its own, not on the back of the last sheet as expected. As a result the mail piece now contains with 6 sheets instead of 5 which creates postage related issues.
The Amyuni component of the printer driver that customer is using has caused this issue.
ResolutionUPDATED: July 28, 2017
Updating to the latest printer driver will resolve this issue.
Product Feature: Printer Driver