I've had that happen too I always kind of assumed that perhaps one of my legs was slightly longer, and/or airflow was slightly better on one side, or possibly my coil was slightly imperfectly mounted OR perhaps it was the way I held the mod, since I usually tilt it in a certain direction or something.
You can see I've pondered it a bit. It's all speculation and because my vape was always fine, I didn't do like, tests or anything.
But yes, it happens.
Anna
It can be the coil, but I find it's usually something to do with the wicking. It means that the wick is drawing more juice from one side than the other. When you open the chamber, you'll probably find that that side of the wick is darker and has more gunk than the other.
If it's working well enough, I'd just keep vaping it until it's time to change the wick. When you change, make sure the wick is even on both sides.
Have you checked out any wicking videos on Youtube? I found it useful to watch a few when I was starting.
I'm one of many vapers who's perfectly satisfied with cotton. If you're interested in rayon then try it out by all means, but you should be able to get a very good vape with cotton.
It sounds like you're not confident in the quality or source of your cotton. If that's the case, I'd strongly recommend boiling it before you use it. Cotton can come with pesticides and other chemicals on it from the plant or the processing. Boiling helps to clean it. Put some cotton in a pot of water on the stove and boil it for about 10 minutes. Then hang it up and wait a day or two for it to dry completely before you use it.
Good luck!