I've noticed two bugs with leveling up mythic equipment. The first is that when I try to unclick something the level up counter goes down even if you click the same equipment multiple times, making it so that I need to add more equipment to level up. Second is that even if you unclick something, it may still use up the material, such as in the instance of auto-selecting. Since equipment leveling doesn't roll over experience like normal leveling, it's just a bunch of points wasted.