The ball winder has 4 nylon gears inside that can collect fiber debris from the yarn that is being wound. As hard as it is to believe, tiny fibers over time collect on the gear teeth and in the crevices between the teeth and slowly but surely bog the winder down.
Any action that tends to slow the machine down and thereby cause the user to exert more force in the winding action can result in wonky balls. This is what happenms, but also the fiber debris does not collect evenly and there will be drag points as the fiber collects in some crevices more than in others. Often times the user will hear or feel a clunking when they go past a certain point while winding. This is due to the fiber build-up inside the winder.
***Note - if the unit is a motorized unit the user may be completely oblivious to what is happening. If the motor begins to groan and moan and the belt slips on te pulley, it is a sure sign that the gears are dirty.
The user will not notice this slowing down action but after they clean their unit, they will see how much of a difference that it makes to clean the gears out periodically.
NKK has a video on its youtube channel that shows you exactly how to do this task.
Click here How to Clean the Heavy Duty Ball Winder
Lubrication - the gears should not be lubricated
The steel shafts should however. The video shows you these locations. Use a light machine oil such as 3 in 1 oil.
Yarn Shops and professionals that use the winder in their businesses should clean them out once per year or even once every 6 months.
Knitters at home should clean them every 3-5 years depending on how heavily they are used.
Additional info on cleaning is available on this link.