Large copter crash on take off pixhawk cube black

After RTL, your altitude will not be at that of your next WP. Won’t you have to first climb to a reasonable altitude, before trying to head to WP20? Not familiar enough with any post RTL options, but maybe there a min mission altitude that can be set for such cases.

The thing is it worked pretty well on simulation. And also when you press resume mission MP will give new mission to FC and in the new mission there is a new take off and all those wp that was done before will be cleared and wp 20 will be consider as the first wp. But before that there are few other commands such as take off to 3 meters and set servo and set speed.

I’m moving back to my small copter and gonna do bunch of new tests and see the results

We have finally found the main problem.
One of our motor did in fact failed to start up. After numerous bench test and trust test. Two motors were identified to have issue.
When pwm is raised slowly from 0 to 100 the motor had no problem and would run perfectly. However if we were to instantly increase the pwm from 0 to anything above 80% then the esc would cut the power and the motor wouldn’t run… That’s what happened with our crash. In guided mode pixhawk somehow run from 0 to 100% max and the crash.
After contacting Tmotor regarding this problem they have come to the conclusion that their esc firmware had issue and they have released the new firmware and I’m gonna upgrade the firmware and do few more bench test and see the results. You can see from the video below how the motor will fail when you raise throttle quickly.

Checkout this video of bench test
https://drive.google.com/file/d/18bt1Tdk__0eBUbTajh_NeG7IIcJ5IkWE/view?usp=drivesdk

No access to the video

@xfacta I have updated the link. Thanks for the heads up
https://drive.google.com/file/d/18bt1Tdk__0eBUbTajh_NeG7IIcJ5IkWE/view?usp=sharing

And for updates regarding this case.
We have updated alpha esc embedded in p80x motor holder with t motor data link and we did numerous tests including bench test and raised throttle from 0 to 100% with many different variations and its finally fixed.

I can safely conclude that the crash was caused by a buggy firmware installed on our esc. Thanks for everyone who helped and gave comments. If there is any other questions regarding this matter you make ask me. Oh and tmotor didn’t take any responsibility regarding this matter.