STM32F302CBT6 as bldc motor speed controller - failing to start the motor

[FBhat.2]

I have custom design PCB using STM32F302CBT6 as bldc motor speed controller with back emf. Half of the boards are failing to start the motor. After a power cycle motor start one time with PWM signal from 0.8ms to 2.2ms then after pwm goes to 0.8ms (motor stop) now the motor fails to start when pwm is increased above 0.8ms