Atmega32u4 tricopter servo problem

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What steps will reproduce the problem?
1. Use NanoWii (Atmega32u4) in tricopter mode

What is the expected output? What do you see instead?
Right after I plug in the battery the servo goes crazy and eventually heats up. 
I can move the servo with my fingers and it doesn't respond to control inputs. 
Twitching is the same on 50 and 160Hz, but much faster in 300Hz.

What version of the product are you using? On what operating system?
Tried with 2.3 and 2.4. Same results.

Please provide any additional information below.
I tried two different servos, no change. I also tried to power the board and 
the servos in different ways, with the same result. However, if I power the 
board first through a USB cable and plug in the battery after the FC has 
initialized everything works fine. I can even disconnect the USB cable and fly.

Original issue reported on code.google.com by [email protected] on 22 Mar 2015 at 9:11

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So, I hooked it up to an oscilloscope and found out, that the servo signal is 
very chaotic until the board finishes initializing. It stabilizes on the first 
of the triple "initialized" beeps.

Possible solutions:
1, Only start outputting the servo signal, when the board finished initializing.
2, Use HW PWM.

Original comment by [email protected] on 10 Apr 2015 at 4:20

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If I disable GYROCALIBRATIONFAILSAFE the twitching goes away just before the 
three beeps.

Original comment by [email protected] on 10 Apr 2015 at 5:24