MWii 2.1 tricopter yaw issue

[markusb]

Had a crash a few days ago. The rear motor seemed to glitch out, although Im not really sure..
http://www.youtube.com/watch?v=M9AnnoDh42c&feature=plcp

Repaired the multi and right now Im putting the last parts back on.
I just noticed something strange.
If disarmed, yaw response from stick is good. Servo centers when I let go of the stick.
If only armed, same thing, centers good.
If I add a little throttle weird things happen. If I move yaw stick and let go, it does not center. It sticks at either ~1400 or ~1600 depending on direction stick was moved. Why is that? If I lower the throttle to zero the servo jumps back to 1500 in GUI.
If I move the tri the servo responds smoothly and then moves back to 1400 or 1600, never 1500.. I have to move it to 1500 with yaw stick input.

Tried another servo, tried another lipo, reprogrammed arduino, cleared eeprom, tried another FC board (same as this one, arduino + MPU6050).
Removed MPU6050 LPF, changed LPF, removed MMGYRO, tried everything I think! Problem remains.
Im not sure this problem wasnt there before, maybe it was. But I did notice it when rebuilding after a crash.

The only thing I have not tried is changing Rx. I dont think its the problem as the GUI shows yaw stick returning to center all the time.

Any ideas about this?
Maybe someone also has ideas about the problem leading to the crash in the video?

[Alexinparis]

About your crash, it seems to be a "motor stop" situation. maybe a bad motor+ESC combination

About the non 1500 centering effect:
http://www.multiwii.com/faq#The_motor_o ... l_RC_input
Try to zero YAW I term, and you will recover 1500

[markusb]

Thank you Alex
Is yaw supposed to be at 0? I will try that.

Regarding the motor/esc combo, its plush 18A and DT700.
Do you mean a bad combo or bad as in damaged/broken?

I have had about 30-40 flights with this combo and no issues at all. Before I had 2213n motors and experienced stopped motors a few times.
DT700 is for me more reliable but maybe not enough?

I have another question, its regarding MPU6050. From time to time I try new ways of mounting the FC to reduce vibrations but NEVER ever get it good enough to run without LPF set at 42 or 20Hz and also MMGYRO activated. If any of the options is not activated the tri wobbles extremly fast and lacks power to get of the ground.
I have tried searching for answers but cant find what I need. Is the MPU6050 really that sensitive or am I doing something very wrong?

Wooden arms, balanced motors, balanced props, FC on following sandwich, HK velcro|HK foam|moongel|HK foam|HK velcro|1.5mm glass fiber frame plates. Before only FC|HK foam|frame.
If I put my finger on the gyro chip I feel a slight buzzing but no real vibrations.

The LPF and MMGYRO seems to give me small small random twitches/jumps/jerks, very annoying in HD footage.
Video recorded when no wind at all. Look closely, small twitches every now and then..
http://www.youtube.com/watch?v=2b-Iid-Fkyg&feature=plcp

[UndCon]

Are you using bullet connectors?

if so - get rid of them and solder all wires - they caused a number of crashes on my Quads

[markusb]

No bullets, solder all power connections.