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LT3796 EVK issue

We have got LT3796 ( DC1706A ) & LT3756 ( DC1319B )EVKs and tested the PWM dimming behaviour.
Here are the test conditions and observations
We use 24V input, 48V LED output and all other configurations are as per EVK default.
Observations on LT3756 EVK:
We have not faced any issues in dimming operation tested PWM freq upto 150KHz with switching frequency at 700KHz.
Observations on LT3796 EVK:
Observed LED flicker initially and it got stable at PWM freq 150Hz and 1KHz with switching frequency 300KHz.
N-MOSFET gone bad when we changed PWM freq to 5KHz and above
Then we did a simulation with the same configuration using LT spice and found Mosfet gate switching is proper and noticed huge inrush current flows through Drain to source.
We would like to understand why this abnormal behaviour in LT3796? let us know if we miss anything here.