Chosen Solution
My Switch unit has a slightly mis-shapen rail, in that the ‘prongs’ which hold onto the joycon, are uneven by just a hair. This allows the joycon to wiggle slightly when in handheld form. I’m not sure how sturdy the metal they use is, but I wanted to find a way that I could fix the rail, without having to send my unit in, and lose all my progress in my games. (Why Nintendo. Why.)
Just to be clear I would send it in if I were you. That being said, if those metal channels are bent you can use a small pair of needle nosed pliers to bend them back in place. Just be sure to put something between the rails and the pliers so you don’t mark up the rails…you could use a thin cloth or thin cardboard. You’ll have to be very careful and bend with precision to get it in the form it needs to be in. This is no easy task in most cases so that’s why I would just either exchange it or send it for repairs. Hope this helps.
What I did for a friend’s switch was bend it into place with very small, pointy pliers while checking if the joycon still fits or if I overbent it. You have to be careful though, the metal isn’t the best, just like any metal part in the Switch.
