If you get offered a bouncy weapon from getting bronze with a golden finger, but you aren't ready to take it and discard it, because you want to prioritize filling your weapon slots with other weapons first, and then you later take that same bouncy weapon from a candy box, you won't be able to level it if you have nothing else left to level.
-You get bouncy weapon from golden finger and discard it.
-All weapons and passives are brought to max level.
-You take previously discarded bouncy weapon from candy box. It acts like it's banished, but it's not.
-It will not level from chests and the level up menu will not appear when getting enough exp.
-The level up menu will only open for the previously discarded bouncy weapon if you have at least 1 other weapon or passive you can level. So getting another item from candy box or arma dio will let you now level the bouncy weapon.
This might be the case for all items that are picked up and discarded and then later obtained through other methods. Can't level it unless you have at least 1 other thing to level. Haven't tested it with stage items.