Quad yaw unstable

Please, help me with fixing issue of my quad. It’s big one on stretched tarot 650 frame, with Gart ML5010/300KV motors and 16" props. After take off it’s randomly rotate around vertical axis and drift aside, even in loiter with good GPS position fix. Auto analysis warn on motors out of ballance, but i’m not sure what can provide such effect - all motors carefully aligned, all ESCs programmed on same min/max signal values and other settings…
Log of last test flight attached.00000100.BIN (1.8 MB)

Have you check motor mounts? Sometimes they move and lose their angle. I had a similar crash, motor mounts were not angled well.

It was first advise which i’ve got there. Double checked mounts, all motors sits tight.

How did you arrive at the YAW PID values you have? Stabilize and Rate yaw P is very low. Did these come from an Auto Tune?

Pitch and Roll from autotune, Yaw from previous setup. Will try to autotune yaw too, but autotuning it usually gives me very rapid turns in old versions of firmware.

Rapid yaw rate can be addressed with another parameter (ATC_SLEW_YAW in centi-degrees/sec). If you plot DesYAW against YAW in your log it shows large uncommanded oscillation on the yaw axis indicative of poor tuning.

I agree that the yaw PIDs are likely not good. Maybe try restoring the yaw PIDs to their defaults:

ATC_ANG_YAW_P 4.5 (was 1.0)
ATC_RAT_YAW_P 0.18 (was 0.1)
ATC_RAT_YAW_I 0.018 (was 0.87)

The motor imbalance, as mentioned above, is likely caused by a leaning motor. The counter-clockwise motors (front right, back-left) are running high meaning that one of them is leaning to the right or one of the clockwise spinning motors (front left or back-right) is leaning to the left.

By the way, I’d like to re-iterate that it’s best to stick with the stable firmware (AC3.4.6) for new vehicles. Jumping to the beta firmwares obscures whether the issue is a beta firmware issue or a vehicles setup.
I understand that it’s easier to get support on AC3.5 because there are more developers responding to support calls but this also diverts the developers limited time away from the very important task of getting the beta release sorted out so it can be released to everyone.