Hexarotor flips over in Stabilized Mode before takeoff

Hi, I’m an absolute beginner with PX4 and drones in general.

I’m currently building a small hexarotor with custom frame for my thesis. As FC I use a Pixhawk 6X (Standard baseboard). It’s designed to fly indoors, so it doesn’t use GPS. To compensate for that (I need to use Position Mode) I’m aiming to use optical flow, the Ark Flow module to be exact, but due to persistent problems with v1.14 beta it’s currently disabled and I only use the LiDAR of the module for better height information.
The Pixhawk is attached to the bottom of the frame with a roll of 180°. The propulsion system consists of T-Motor F2203.5 2850KV motors, Gemfan WindDancer 4032-3 props and T-Motor ESC F 35A BLHeli. Power comes from a 4S 2600mAh LiPo together with the Holybro PM03D power distribution board. The motors are used in a pusher configuration (facing downwards).
I use QGroundControl Daily Veryion master:aa0f2c61b 2023-06-14 13:09:56 + 0200. Firmware is v1.14 beta, Generic Hexacopter X airframe.

Today I did the first flight test with the drone attached to a safety rope. This is the log file: https://review.px4.io/plot_app?log=2da554c8-855f-4996-a0f7-d77824dba78f
I use an RC to control the drone and have it connected to QGC simultaneously for quick changes and general observation. Flight was performed in Stabilized Mode. After arming everything seemed normal and I started to rise the throttle stick. At a certain point (way before 50%) the drone basically flipped over and rotated around all axes. After the flight QGC showed a Gyro error, which can also be seen in the logged messages (basically all IMU with clipping).

One logged message after takeoff says “[health_and_arming_checks] Preflight Fail: Attitude failure (roll)”. I observed all sensor values to be normal, both via the altitude/compass display in QGC and via MAVLink inspector. So, what could be the issue here?
Another thing which I think is also important to mention is that the drone’s legs bend a bit in their current design, which causes the drone to vibrate a bit while the motors spin. I think the small divergence of X and Y local position seen in the log might be related to that. However, I don’t see how this might be related to all the attitude issues.

I would really appreciate some help with that and also suggestions on what I could change in my setup (e.g. use other flight modes for testing).

I had a drone flip over as soon as I throttled up in Stabilize once.
I connected the motor in the wrong order, can you check that your motor order is correct?
Airframes Reference | PX4 User Guide

I recently did a few more flight tests in different modes. Since they all showed pretty much the same results I decided to open another topic focusing more on interpreting the logs Hexarotor flips during takeoff
As you said, it seems to be an incorrect motor order. In my recent reply there I tried to explain my approach an make clear where I went wrong. It seems like the rotation of roll=180° that I set for sensor calibration is not used globally. So due to this, my motor order from a top view of the drone is mirrored along the x-axis.

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