Hi, I had a similar problem with Microsoft Dynamics 365 for Finance and Operations (8.1) platform version : Update22.
The error message was : The transaction on voucer xxx do not balance as per 22.01.2019 (accounting currency -0,01 - reporting currency -0,01)
The number sequence for project invoices and invoice vouchers are all set to the same continuous sequence. One number in Status list was Free.
After deleting the free number and running a manual cleanup I was able to post the project invoice.