Sketch glitches

sketch glitches. The story is like that. Nano is standing in the car. controls the servos. under some conditions it is incomprehensible to me that there are glitches for controlling the servo. one runs from 0.6 -0.9. another 0.4-0.1. nano reads the input voltage through a step-down regulator to 3.3. via digital read. until the servo light is turned on on the car, keep the values ​​0.5. when the light is turned on, the value is read from gy-521. and so it happens that both servo stand in position 0.1. although by condition one of them should not do less than 0.6. after reboot everything works fine. board power also through the stabilizer 12> 5 v.