Your stick is malfunctioning, it is quite normal.
I use the Extreme 3D Pro's, in my heyday they would last an average of 3 months before getting "jitter".
I got to the point where I took a photo of a wheel barrow full of them and sent it to Logitech, along
with a letter asking them to revise the design, or drop the price by 75%, which is all they are worth....
I never got a reply.
Unfortunately, I am hooked on them by the layout and ergonomics, so I keep buying them.
Some seem to last better than others, maybe a year out of one and then a week or two from another.
My neighbor went to the rubbish tip's recycle centre and bought one for a couple dollars, he then gave it to me.
It's lasted almost two years now, after being someone else's trash, so go figure.
I have read that fine carbon dust accumulates on the pots/brushes whatever, and they can be cleaned, but
I've pulled a couple apart and I realise I suck at repairing them, I only get so far and just gave up and went
and bought another one.
They can also break the usb cable (invisible damage) where it exits from the stick, but mine rarely last long
enough for that to be a problem.
I reckon I've bought over 30 of these sticks, which is just insane, I know, I just never could bring myself to
spending A LOT MORE on a decent alternative.