ok, i gave up trying to colect all the root nails, 2 in the crystal cave seems to be bugged ;-;
indeed, i got to floor 55 expecting that it would spawn in the upper floors, but nope. Also, is kinda easy to get there with the slime companion, Because it becomes stronger with each potion and there is a glitch that the potions dosent get used if in the companion's inventory but in combat they use it. Grow RPG: Infinity potions