We're using your mod on a modpack with the mod "Numismatic Overhaul" and the coins added by that mod can stack up to 100.

When we place one into a bundle it instantly crashes the game with the error that the game divided by 0. I presume this is because of the max stack size but I don't have any actual proof of this hypothesis.

I did noticed that theres a bit of a safeguard put in place with normal bundles where it doesn't allow you to place the coin in them at all..