Pull the front body pin, seperate the upper body from the lower and pull out the hopup assembly and inner barrel.
Then, take close look at how the hopup looks, and works, before you take it apart. Then, take it apart step by step, making sure you note where each part goes. Start with the main adjuster gear, unscrew it, then the others. C clip holds the inner barrel to the hopup, unclip that last, and carefully pull the barrel out, the hopup rubber will come with it.
The nub, is located under the hopup arm, and sits in a little cut out, make sure you dont loose it, as most do when they take the barrel out.
Inspect the hopup rubber for any tears or damage, this could be whats causing the side spin. If all is ok, clean it with a soft cloth, the assembly, not the rubber. Allow the hopup rubber and nub to soak in some warm soapy water for awhile, then cold water rinse and air dry.
Add a drop of silicon(non petroleum) to the rubber once you have it back on the inner barrel, work it in with your finger, this is just to allow it to slide into the hopup chamber again without corking it or deforming it. Lube for easier penetration!
Then hold the barrel up to a light and make sure you cant see any deformities, any thing blocking the barrel around the hopup inside. If not, put the c clip on, and reassemble the hopup.
If you do all this correct, you should have no issues, and it will shoot alot better. Go slow, and dont be impatient.