Strange low pwm voltage on motor pins

I just installed new T-motor Alpha 80 HV Esc and i have a lot of troubles for them to initialize. I scoped the motor pins and found out a voltage of 1,2 to 1,6 volts across the motor pins. They are at 2,3 when not connected but as soon as i connect the esc they drop to 1,2-1,6 (all for pins are between 1,2 and 1,6 volts).

Swapped Pixhawk 2.1 with a new one and all is normal and i see 3,3 volts with esc connected and esc behave normally.

I came to the conclusion my first Pixhawk 2.1 is shot. How can that happen so that i try to avoid that in future?