Question about Neurons in Nengo

Hi everyone.
I’m new to Nengo and have a question about the randomness of the spikes generated by neurons.
After specifying encoders, intercepts, max_rates, and neuron_type, I got an ensemble of two neurons with the same tuning curve. I thought the spike trains generated by the two neurons with the same input should be the same. However, the spike trains are different for these two neurons. What factor caused the difference in the spike trains? Except for the parameters I already specified, is there any other variable that determines the activity of the neurons?

I would appreciate any help on my questions. Thanks in advance.