CoaxCopter repetition of SPIRIT drone designs. Tuning

Need help both understanding and tuning the CoaxCopter design.
At the moment, a prototype has been assembled, and it is basically configured as a CoaxCopter. But the first tests and settings are somewhat confusing.
List of accessories:
Motors Tarot 5008 340kv (the design of the shaft has been changed, for installation on a pipe)
Prop DJI 2170 оr custom mount
ESC 50A Blheli32 12s
FC Pixracer r15
Servo AFRC-D3519HB-S BLDC Digital (Standart, Fast 0.07s, For Rc Drift car)
Homemade swashplate
Battery and Current control through ESC
Powering 6s battery

Controlled by two servos with 90 degree placement and 35 degree phase advance.
Control of motors according to the DShot600 protocol. To do this, the channels were reassigned, since Pixraxer only supports dshot on 1-4 channels.
Servo1 - Motor5 (Dshot600)
Servo2 - Motor6 (Dshot600)
Servo5 - Motor1 (400hz)
Servo6 - Motor2 (400hz)

At the moment there is a problem with the PI Yaw axis setup. At the minimum values ​​of P=0.1 I=0.01 there are oscillations, and only when the value is reduced to P=0.05 I=0.01 stability appears, but the YAW control is sluggish.
Since while the YAW is being set up, I can’t set up Pitch and Roll.