You use Acronis Backup Cloud version 7.7 or Acronis Backup 12.5 with cloud management.
You create an Entire machine backup plan and select 'Version 12' backup format. In the exclusions, you specify one of the partitions, for example E:, to be excluded from the backup.
The specified partition is not excluded from the backup.
Issue in the product.
The issue has been fixed in Acronis Backup Cloud 7.8.
Specify the partition as <letter>:/
For example, E:/ instead of E: