Why does my closed-loop response with MPC look like this?

With the above configuration, I want to obtain a closed-loop frequency response using Bode Plot Simulink. My desired range is from 10Hz to 10KHz, but as shown in the below figure

- Blue ------ PI controller closed-loop response

Yellow, Orange, Purple ----- MPC closed-loop responses

Why MPC responses are like that? I want to compare PI and MPC controller responses, but stuck in a problem as mentioned.

MPC controller responses zoom in, I am not sure why responses are like that.