Quadcopter Control Problems

Hello, I’m using the Navio+ on a 470 class Quadcopter. Today it was its second flight and it is having several problems, and I want to hear if there is any ideas to solve them.

After the GPS Lock it started to flight in Stabilize mode, but started to rotate slowly to the left. I tried to compensate the rotation with a full right yaw, but it just stopped the rotation to the left and started very slowly to rotate to the right. For times its seems that it was not responding properly to pitch and roll commands either.

What do you thing I need to check in order to troubleshoot this problems?