You must validate the model files in order to avoid errors being generated in code.
Validation is the process of checking that the model is complete and correct. Validation is always performed before generating code to ensure that no errors will be generated in the code. If errors are found, the code is not generated.
The module.mdmxmi files are automatically validated when they are changed, or when projects are rebuilt.
You can also manually validate a model file from the editor, by clicking Validate Model or selecting Validate model from the menu.
If validation problems do not appear in the Eclipse Problems view, it might be because your configuration of the view is filtering them out.