For all who helped me when crash happened one month ago, I really appreciate all your help and would like to give you all an update.
This drone has a 3-month service warranty after I repaired it in China on Jan 11th 2019. I crashed it on Feb in US, it was under warranty but the problem was: I must returned it to China’ maintenance store to use the warranty and I need to pay the shipping fee from US to China.
I contacted Chinese DJI customer service. They are able to do some remote diagnose from the data in my DJI app (sync to cloud).
Two days later, they responded me that the crash was due to DJI’s problem. I asked someone to take the drone back to China and got free replacement at Shanghai DJI flagship store.
It is good that I got a free replacement but till the end, I still don’t know what kind of malfunction it was, and I still doubt the missing propeller issue was truly due to malfunction?
But anyway, thanks for everyone who provides me help!