As another recommendation: Try to make sure that your non-linear parameters are roughly of the same order of magnitute. If one is, say, between 0.001 and 0.01 and another is between 100 and 1000, Stan may have trouble sampling from the model.
As another recommendation: Try to make sure that your non-linear parameters are roughly of the same order of magnitute. If one is, say, between 0.001 and 0.01 and another is between 100 and 1000, Stan may have trouble sampling from the model.