Hi there!
According to the investigation, this error only happens with Snappy and it means that the mesh is geometrically different from the model. In this case, the regions around the fan are very coarse and the mesh has holes.
The solution here is that you refine the mesh in critical areas. Making a flow volume extraction and using the standard mesher is highly recommended.
If you want to learn more about the Standard mesher, check this page: Standard Mesher | Meshing for CAE | Documentation | SimScale
Best regards,
Fillia