Why brown out

Hi, why auto analysis give me brown out?

Because that log shows you emptying a 6s battery in a little over 2 minutes (going from 4.2v pre cell down to 3.18) and the log ends while your 150mtr up in the air.
If the current usage is correct then I’d say your battery is dead as 750ma is a bit low for a 6s.

Unfortunately you haven’t said what actually happened, what the problem is/was or anything to help you with.