LTC3892 overheating

I am using the LTC3892 for dual 9A 36V outputs. I have noticed that using one channel/side of the LTC3892 everything works but as soon as I turn on the other side the voltages start turning on and off and the the LT3892 gets hot. 

I am powering the chip using and external 12V power rail (extVcc) with the driver selected for 10V.  The switching frequency is 202khz and the transistors I am using(csd18532q5b) have a gate charge of 44nC at 10V.  Hence for the two transistors per side there should be around 18mA of current, well below the 50mA spec per side. Also with 2V LDO drop this should only be  36mW (72mW with both sides on). 

Is there something else I should look at with the part as to why it is getting hot?