Is this code or a script or workspace you created and saved? If you can share what you have it might help me answer. I think Zach's pretty busy but this is his wheelhouse so I'll see if he can comment.
Yeah the different biologically realistic neuron models behave quite differently from each other. Sometimes forceSetActivation is useful in the code. Some background on the different inputs types is here
http://www.simbrain.net/Documentation/docs/Pages/Network/neuron.html- Jeff