Starting with the release of Strategy ONE (March 2024), dossiers are also known as dashboards.
When users try to upload a .mstr file in Strategy, they receive an error message.
The error message in MicroStratgy Web:

The error message in MicroStratgy Workstation:

This is expected behavior. An in-memory cube is converted to a DDA-to-IServer cube during exporting due to one of the following reasons.