Building Charlie with Lego Mindstorms 51515

[Pablo H]

Hello. I am building Charlie with the new Lego 51515 set and I am having problems with the drumset activity. One of the arms doesn’t work ok. I know that it it is because I haven’t set properly the 0 positions of the engines, but I don’t know how to solve it. I tried to improve it a lot of times but it’s impossible for me. The head of the robot stay always a bit to the left. Can anyone help me?
 

[David Lechner]

Have a look at 

to see how to calibrate the motors.

[sunspot]

You might also want to take another look at step 21 of building the body, which might potentially be confusing and could lead to something like that.  Note that the inset box is showing you to do two things, not just align the motors but ALSO line up the turntable before meshing the gears. 

[Pablo H]

Thank you very much both for your help. I am not sure what caused the problem, but it is solved. 
I calibrated the motors, rebuilt the robot and it worked ?

I haven’t done it yet because I started building the robot before I downloaded the app and when it asked me it was too late ?

Yo were very kind.