I have 550 quad with Naza m lite with upgraded to Mv2 firware, I had a strange issue with the quad. It was a indoor test and I was hovering in height of 3 feet in GPS mode with 50% throttle for some 5 mins, suddenly the throttle started increasing and hit the ceiling and crashed. Realizing the sudden change in height, I brought the throttle down to 0 before hitting the ceiling and I didnt not even activate failsafe switch. Fortunaly only props had broken due to the crash and no other damage.

Now can anyone tell Why there was sudden increase of throttle, Do low battery trigger failsafe.

My setup
Daya 550 frame
Naza M lite FC with GPS
DYS 4in1 30A ESC
Sunnysky x2216 1100kv Motor
Zippy 6000mah 3S battery (parallel 2 Nos 3000mah battery)
FPV config with Mobius.
turnigy 9x Tx/Rx

Being a DJI product, I assume you cannot take out the tlogs?

And it's pretty dumb to use GPS indoors, mainly because of poor connectivity.
Did you have a 3d or 2d fix, by any chance?

If it were the battery failsafe, then you should've already charged your battery pack.

See how it's programmed in Naza. In an APM, return-to-launch is initiated and the copter reaches an altitude of 10m and goes to the starting position else direct landing.

So, if there was a similar RTL procedure then that must have caused the crash.

Well yes, I was having poor GPS signal due to indoor but I was having GPS lock with green and red LED blinking....

low battery scenario, there are 2 levels protection in the FC at 9.75v and 9.5v  with load,  I didnt remember getting any LED indication.

A poor GPS signal results in poor data passed to the flight controller.

What was your battery voltage just after the crash?

If no signals were detected of failsafe activation, then it's probably the GPS, imo.

Flying with GPS, with a lot of interference is one of the worst things to do. At least, from now on, you can take care of that.

It may also firmware issue as bcoz  naza don't have official firmware upgrade to v1 or v2. Naza v1 can be officially upgraded to v2 with some limitations but not m lite to v1 or v2 its unofficial and also as you stated you are flying indoor with poor gps signal. So may be its consequences of both.

Yeah, completely forgot about that case. That's an illegal modification

And that's completely unofficial. So, that might be a reason. Probably a bug.

But its great that you have saved a lot things.

may be Firmware issue,  Now I have downgrade to default firmware....