I have a Super Mario Odyssey Switch and I have always had problems with the joy cons. I have already sent them in for repair and they gave me new ones. These ones were way worse. The problems were on these too, but these ones also had some different problems. I fixed pretty much all of them, but one:
The left joystick keeps drifting upwards, even when I'm not touching it.
I tried everything you could think of, and nothing worked. I tried using a pipe cleaner to clean under it and it works better, but not fully. Any ideas? I have not had the switch for a year so I could send it in.