To ensure that your submodel generates a valid solution, you should check the following:
You should check that the position of the submodel is correct, relative to the global model. You can check the relative positions in the Assembly Design workbench before you submit the submodel for analysis by creating temporary instances of the parts in the global model. You can view the position of the assembly in the global model relative to the position of the assembly in the submodel. You can then delete or deactivate the instances of the parts in the global model before you mesh and analyze the submodel.
You should check that the submodel response has insignificant impact on the global response. This is the fundamental assumption of submodeling.