Service Request Attachment Privilege missing "You do not have permission to add a new attachment."

Hello Community

We have a Custom Role for Service Requests. This Role should be able to create all the different Service Request Messages and be able to attach Attachments to the different Message Types.

The Role has already the Privileges:

Add Attachment

Download Attachment of an SR or SR Message

View Attachment

And the Role:

Attachments User

The creation of Messages works fine, however for the attachments we receive the following Error:

Any Ideas of missing privileges?

Thanks in Advance

Kind Regards

Maxim