I have had similar problems with different types of joystck Hardware in the past.
If the axis effected is your rudder ,ie:twist axis then the potentiometer is worn or dirty.This is a rotary electrical device that sends the rotational position from your stick to an onboard chip .In turn that sends data for your software to interprit which in turn sends that interpritation to the programe you have running.
You have four options,
one: replace the stick which is the safest by far,
two: use rudder pedals and dont use the twist axis.
three: try to clean the pot.
four:the last option is temporary and been sugested already,to increase the deadzone in the calibration section.
As I am not familiar with the positoning of the pot in your hardware you will need to see if the pot is in the base or the sticks handle.That is done easily by looking between the stick and the base at the shaft that protrudes from the handle & dissapears into the base.
If the shaft rotates then the pot is on the end of the shaft in the base.If the handle rotates but the shaft extending into the base remains staitionary then the pot is in the handle of the stick.
Firstly power down and dissconnect the stick. You will have to strip the stick to get to the pot in question so check to see what type of fixing driver or allen keys you need.Get some electrical switch and contact cleaner from your local auto parts supplier or electrical shop.I have used Wd 40 at a push before ,but you must make sure to get the access out of the pot. Where as the electrical cleaner
will evaporate.Once you have access to the pot remove it from its fitting trying not to break any connections.Spray the cleaner into the pot and move it from one end of operation to the other .Keep repeating this untill it feels smooth then dry out and put everthing back together.
This is totaly at your own risk as I have heard of someone who shorted the usb feed and blow out their usb circuits in their system box.
Additionaly it can be a good method to take some piccies as you go so you have reference for re-assembly.Good Luck
