The BSIM 3v3.2 model has 152 parameters to specify the transistor. The newer BSIM4v5 has over 200. Frequently model parameters are not fully specified. If not specified, the model uses an ideal default. Problems there are generally associated with the parameters entered into the model.
Often heard is the comment that these are poor quality models. Not always true. Generally the model is not the problem, but the numeric parameters entered into the model.
For more on how Effective Electrons can help troubleshoot BSIM Transistor Models contact us.