Although this bug is much less common then it used to be, it still happens. this bug happens sometimes while enchanting, and it is not fun. It can easily ruin an enchanted book with an enchant you've been saving up for, ruin a perfectly good sword by having knockback applied to it, which makes fights 10X harder, or have a massive cringefest every time you hover your mouse over your pickaxe and see Unbreaking III. You get the idea. This glitch sucks.