My experiences were Copter: Parrot AR.Drone, Phantom 1 and II So I can deal with those things..
Make no mistake, I have a checklist packed me on smartphone, I'm meticulously gone through before each start. So well that night in June.
First, the copter flew in windless evening light on the Baltic Sea. Without advance warning, he suddenly keeled over after 2 minutes flight time away to the side and took off across the water. First, I wanted him (he was about 3 meters) bring the level to gain some time - he did not react. Then a few times gently pulled the sticks, he barely reacted, but you could see the wegdruften just a little slow.
As a last resort, I had asked the Failsafemode on GoHom and country. So brave the remote identified. He did not respond, but flew away, only to clap with an overhead rotation of the water. No chance for me to get him out again.
First I wrote to Conrad (bought it via Amazon there) that refused any cooperation. Finally, I had to "show" the copter. Too bad, because if so falls into the water part of it is gone.
Then directly contacted DJI. Friendly they sent me a table with questions that I could answer all of them. Only to the LED display on Copter during loss of control I could not say anything exact, I finally had enough there to do than to document lights.
After I sent the list back, nothing came.
Nachgehakt After weeks. Answer: Thank.
Nachgehakt After weeks. Answer: Thank.
Nachgehakt After weeks. Answer: Thank.
Nachgehakt After weeks. Answer: Thank.
Then after I nachhakte emphatic, I was offered a small discount when purchasing a new DJI Copters. That's it.
One week after this pitiful offer came a promotional message: "Tell us your story DJI". Here it is now.