There is probably a server-side exception. You can check Radzen's Output window to see what it is. In addition you can attach a debugger to the server process.
System.InvalidOperationException: The EDM instance of type '[Prj187SoterMaquinas.Models.SoterMaquinas.TUcNegocioViatura Nullable=True]' is missing the property 'Negocio_Id'.
but if it is nullable it would not need the field that is external key.
Maybe the only workaround will be to remove the relation from the data-source meta (look for x-foreignKey) or ignore the model in server/Models folder and remove directly the attribute.