Need help in analysing my Copter Crash

ArduCopter Copter 4.1
1

I had a crash with my copter running Copter-4.1.5 in guided mode. It was flying in guided mode and after a few minutes of flying, it crashed.
After analyzing the log I found that for a moment voltage dropped to around 5V and again it came up to 14V.
Also POWR.Vcc dropped to 3.5V during that time.

After the crash even I checked if all motors were fine and all motors were working perfectly fine.
The connector which I am using as a power port is XT60.

Initially, I suspected that it could be due to sudden power loss in mid-air as it was a windy condition. But in that case, a log should be recorded up to mid-air only.
Since the log is recorded all the way up to the final crash on the ground, what could be the reason I am not 100% sure?

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https://drive.google.com/file/d/1o1tADhRcEp81z7v-LX9vj_osMI7DyWgs/view?usp=sharing

2

I didn’t look at the log but here’s my thoughts. Given that the current dropped as well, I would focus the search on the battery, power connections and power distribution. I suspect either an open connection or voltage regulation failure down stream of the current sensing, or a short up stream of the current sensing. And as say this “out loud” I’m leaning more to the idea of a short upstream of the current sensing. That would explain the massive drop in voltage but no significant measured current flow. Check all your solder connections. Look for burn marks or dark patches. And smell the board. When the magic smoke comes out of electrical components it leaves an odour.