If you can share your model or other reproduction steps, then we can likely offer better advice. In the absence of those details, one thing I notice is that the rate equation you provide could easily result in non-finite values. For example, if TumorCarryingCapacity is ever 0, then the log term will be -inf (assuming a positive, finite value for TumorVolume). If r or TumorVolume is also 0 at the same time, then the rate will be NaN.
You could use the SimBiology Model Debugger to step through your simulations to see if non-finite values appear and determine what their source is.
