My quadcopter is taking slow yaw after take off(Please help)

Hi I’m having a problem. please help…While taking off and after taking off my quadcopter is taking with small angle. It continues to take yaw while it flies. I saw videos of APM quadcopter and I never seen such behavior. Any idea why this is happening? Please help.
Here is a video link of My quad flying in google drive . I am sharing the link. Please watch it and tell me what could be the remedy.
link: … JEMG8/edit

That does not look like an original 3D Robotics quadcopter. This subforum is for original 3DR RTF copters only!

yes thats a Bumblebee frame. And I have mounted an APM 2.5 there. please tell me what could cause this yaw? I am really getting frustrated with it. Thanks in advance.