These Switch owners experience what’s been called the Joy-Con drift. It’s named after the phenomenon where player characters move without any input from the player themselves. And as mentioned, it happens more frequently with the left Joy-Con.
These are caused by wear and tear, but the issue is that it is reportedly happening too soon. A Reddit user has reported that their left Joy-Con started drifting after four months. A breakdown by another Reddit user shows that the contact pads in the Joy-Con’s circuit board are made of a softer material than the metal prongs of the analog stick. For those who remember, this was also an issue for the first generation DualShock 4 controllers for the PS4. Sony fixed this with the newer controllers – the ones that have a strip on the touchpad allowing the LED to shine through. Nintendo, on the other hand, doesn’t seem to be doing anything about the Joy-Con drift at the moment. This will be especially worrying for those who plan on getting the Nintendo Switch Lite, as it doesn’t come with detachable Joy-Cons. (Source: Reddit [1], [2] via iFixit.)
