When you open the Skins tab, it freezes the Launcher. I don't know how many skins are needed as I only had the problem when I had at least 15 skins. And because skins can't be removed from the launcher outside, it will keep happening. Again, I don't know how to get to the folder for all owned skins, if it exists.

Edit: Video Evidence Below (No Audio but I was clicking to prove it)

Edit 2: Has to be in Vanilla, no Mods in-game.