Strange incident. Need help

[brat002]

Hi all.
Today I builded new quadcopter on M4+N4(broken SD card slot. No logs.)
Warthox with custom alu arms
MT2208
KISS ESC 18a
DYS Smart 3 gimbal with Storm32 controller
pids:

After some pids tunning I got stable flying, but... After 5-10 minutes of flying in position hold mode i had 2 identical incidents. Quadcopter starts twitching and fly away. Switching to manual mode solves problem some time after switching.
Here are video of problem:
https://youtu.be/L3037XR7I5M

What is it and how to fix it?

PARAMS.txt

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[kinderkram]

Without a log file or telemetry connection it´ll be hard to investigate on this incident.
That behaviour could be caused by a variety of malfunctions, starting with the radio setup, bad GPS receiption or a loss of it during the event.

You should at least have a telemetry connection, monitoring the radio quality and the GPS accuracy while flying in PH.

[brat002]

Mobile phone was connected via bluetooth. No any alerts in this moment.

[LPR]

I mounted the X8R FrSky receiver way to close to the GPS antenna and I had problems similar to yours. Moving the Rx, 4 or 5 centimeters ways solved the problem for me. The Andriod app has the value for Hacc on the main screen. If you see that the Hacc is greater then 1 m/s then there's likely a problem with GPS reception.
On a ladybird quad I've had poor GPS reception with the bluetooth module too close to the GPS antenna.

With tall building around blocking GPS signals, your GPS reception needs to be the best you can make it.

Larry

[aBUGSworstnightmare]

Maybe with to post some pictures of the craft. As already pointed out, it's hard to tell without a log file.

[brat002]

Frame currently is partially disassembled. Here are photo before first incident.

Gimbal mount is my nightmare, but it sits stiff.

[aBUGSworstnightmare]

[brat002]

I performed mag calibration and problem is not reproduces.
But here another problem with pids. Copter starts oscillates on descent. Cant find solution for fix it.

[aBUGSworstnightmare]

[LPR]

I found that not having the battery mounted so it will not move around during flight is very important to have good control. The more solid the battery mount the better for reducing vibrations to the flight controller and to the camera.

Larry