Don't have this Load device but been down the Cheezeball equipment road a few times
So take this lightly
If the Power MOS device gate is being taken out by over voltage oscillations as mentioned, if so, this is likely due to a feedback issue caused by the Power device "Miller" effect. Using higher power devices will also increase the Miller effect capacitance, so some form of compensation may be required. Placing a lead capacitor around the series gate drive resistor should help, also if a series resistor with the gate driver input, use a lead cap here. Protecting the power device with a Zener is a good idea, and protecting the CPU pin with a series resistor (or larger value if already used) may help, use a lead cap around this resistor as mentioned tho, otherwise you likely will have a big high powered oscillator!!
Anyway, good luck with getting this Cheezeball loads working for reasonable bench use.
Best,