Received a text message from Corey that ITMX mode 13 was rung up and the nominal settings was making it worse. Corey tried increasing/decreasing the gain settings without any luck. At this point I applied the following settings to try and damp the mode,

Gain = -1 phase -90 degrees - increases
Gain = +1 phase -60 degrees - increases
Gain = +0.1 no phase - increases
Gain =  +0.1 +60degrees - increases

The above settings did not work and the one shown below seems to working for now as shown in the plot,

FM1+FM2+FM4+FM10 gain +0.1 (phase -90 degrees). After some time I will try ramping up the gain to see if I can bring IX13 down at a faster rate.