1. Backup fails with "Internal error"
2. You expand activity details and in the line "Stream name" you see a file with .tibx extension that points to format 12 archive, for example:
| error 0xa100fc: Stream name: 'ARCHIVE-91CB9821-8079-4E91-AD42-57DBC14A0D1E-7E0D9791-3A27-44F0-93AF-775E44C8CB84A.tibx'.
The issue is under investigation
Please collect Acronis System Information from the affected machine and contact Acronis Customer Central with a reference to this article.