IMC control for multivariable nonlinear systems

Hi, I have programmed an imc controller for a mimo nonlinear system in Matlab simulink. The system has 3 outputs and 3 inputs. The control runs so far. However I have 2 problems

1. 2 outputs are controlled to the setpoint. However, one output does not reach the setpoint. x1 does not reach u1.
2. if I add a disturbance, the system does not control and the simulation hangs. Here I noticed that the choice of the filter is important. However, I can only control one output with the correct choice of filter. x1 does not reach u1 and x3 does not reach u3