The designer validates the model within the project (against the schema and roles that are present in the project). If validation shows no errors, the model is correct within the project.
The situation from above is typical for the case when a project is taken from one project and deployed in a system with a different schema or roles. For instance, the Initiator role that is defined in the project in designer does not exist in the system where model was deployed. If that happens, management studio will show the error that "is not detected" in the designer (since the project in designer does not fit the situation in the system).
If you observe a situation like this, either
- create a new project from system snapshot, where you can correct the errors and redeploy the model/schema.
- or, take a snapshot of the system and look at the validation of affected model to understand the issue and decide how to proceed.