H520 Fly away.... Help identifying the issue needed!

First, Where has Yuneec USA gone? No phone numbers, website has no ability to setup a call....


Yesterday while flying a test flight (I was trying to test the battery switch when flying a way point flight plan) I lost control of the drone.
I am looking for some help identifying what happened. This drone was a replacement last year (flying missions that required battery changes failed to work at all - controller and drone would not be able to continue at all after the battery change) that I have hardly used.

The first flight went well, battery depleted and the drone returned to take off point.
Switched the battery and tried to continue the mission but the mission restarted so I landed and selected the way point I believed the drone reached with the first battery.
I manually took of (I think, might have been the previous take off) and then selected to continue the mission, very shortly after the drone started flying very erratically. I tried repeatedly to cancel the mission and take control, the controller was repeatedly saying " Returned control to pilot" but i never regained control.
Once the drone crashed, I found that one of the motors was still turning even though the drone was on it's side.

This is the flight log from the airframe. (the flight log from the controller was corrupt and so far i haven't been able to open it).
https://review.px4.io/plot_app?log=869614a2-1bdf-4ba4-8685-cd884ef3d736

I have a mission to fly with this drone on Friday so i have to get some replacement parts fast (an arm is the main part) and then some testing providing someone can give guidance on why this happened.

 

Turns out the tlog file I thought was for this flight that was unreadable was for another flight.

I have attached the tlog file (with txt extension to get it to upload)

 

There are a number of logs stating changes to do with rotor mode's and various "motor stalling" but they all started at 5:06.
5.06 is where the aircraft landed and rolled

Using UAV Toolkit i was able to see what the controller thought the aircraft was doing but if you compare that to the file from the aircraft it is completely different from the point it lost control.

 

Thank you for reviewing this data.

You are correct, the file contains data for 3 flights, the last being the one with the loss of control.

I distinctly remember looking at the controller once the new battery was in and the drone started up. For a short period of time it still showed the 18% or so of battery left but then went to 100% so i'm not sure why this was not recorded correctly but might explain why i wasn't able to continue the mission correctly.

The critical 'Failsafe enabled' i believe was a few seconds after i had issued the command to continue the planned mission from the point i had selected.

At around 5:02 I think I forced the Datapilot to close in the hope it would allow me to take control but 4 seconds later the drone was on the ground.

"Is it the one you described as flight as last flight?"
The mapping is kind of close to the actual flight.

I do not know if the GPS signal was lost because of the angle of the drone as it really was flying very erratically - steep banks to the point at one stage it looked like it had flipped.

I have since flown the drone in a large open space, first with a rope on it so there was no way it was going far but after a while of seeing no issue I flew without the rope a little further - about 300ft away. All of a sudden the drone reported loss of controller signal and was returning to home. I looked at the controller and everything looked good, I was still pointing the boosted antenna in the direction of the drone as it returned to me next to the take off location but the control never returned even once the drone had landed next to me. I tried resetting everything and the connection returned. I swapped out the ST16S for another that I have and was able to fly without any issues at all.
So currently my conclusion is that the combination of trying to return to the planned mission, some sort of loss of the GPS signal and then me trying to take control with a controller that is not functioning correctly resulted in the aircraft going through a loop of trying to return the control but failing so trying to run the mission again but with no GPS signal so the aircraft started trying to just land where it was while flicking through these states repeatedly. There was a fair amount of wind, around 6 to 8mph with some gusts which just added to the problem.

Any suggestions on what to do with the ST16S? Is there a way to test it or for me to get it repaired?