The first time (with frame IMU) board reported many I2C errors. I noticed, that the problem occurs after YAW motor set up some power. On the advice of my friend, I tried to put YAW cable through the ferrite ring (a total of 4 turns). Now I have about 3-4 I2C errors per minute and stabilization works quite well.
I guess I'll try to put ferrite rings on all three engines and probably more than 4 turns....
