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We've had failures like that.
The cause was the MOSFETs shorting the gate to the drain during failure, applying pack voltage to the gate driver circuit. The underlying cause was counterfeit IR MOSFET from a Chinese supplier, which had far higher on resistance than they were supposed to have. Our previous MOSFETs failed shorted, or ejecting the bond wires out of the package top (explosively) but usually leaving the gate insulated. These destroyed something on the gate driver board every time they failed.
Your root cause might still be a noisy gate signal causing overheating (we had issues with staccato turn-on cycling when using optocouplers), but the TVS explosion probably occurred after the MOSFETs failed.
We figured out during prototyping that putting a TVS on the gate driver output (vs. on the MOSFET side of the gate resistor) would result in the gate driver resistor acting like a fuse, often saving the gate driver and reducing the rebuild time.
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