2nd Maytech 75_300 burned

Hi,

Today for the second time I burned a maytech 75_300  with:

12S liions

Motor Hacker Q80 8M 8m

drived via pwm

freq at 50Khz or 60KHz

Ctrl : pid speed no reverse

Current limits set to +-160A

erpm final consign at 100360erpm

no breaking 

the pwm from my autopilot increase from low duty to high duty cycle in on step, i'm using a 40 seconds rise up inside the pwm app to have a smooth ramp.

When the power rise around 1400W, the Vesc stoped the engine by itself without any error (despite the pwm wasstill at its high value)

30s after, the engine was always off, I set back the pwm to its low value(idle). I heard a clack followed by a bad smell . That was the mos. It stoped the power security of my drone. Now The Vesc power cable + and - are in shortcut ;-(

To resume:

First, I don't understand why the Vesc stops alone during the rpm increase(power security?) since there are no error in the Vesc status.

Second, why it burned after 30 seconds after this unwanted stop, and just after I changed the pwm input from high to idle.

Advises are welcome,

Thanks in advance,