Steps to reproduce:

1. Line up 4 mana pools with mana in a square formation next to each other.
2. Drop 1 iron ingot right in the middle of the 4 mana pools.
3. Result: 4 manasteel ingots.

Haven't tried with alchemy catalyst, etc. but I reckon it works the same.

Forge: 2282 and also tested on 2285, both server and singleplayer
Botania: R1.9 343
Also used JEI and latest baubles and autoreglib as of this post. No other mods.

#2228

I dropped iron ingot with Q (default keymap for drop item). Might not work when dropped from inventory.

found it, stack.isItemEqual doesn't check empty state -.- so the recipe matches even when the stack has been invalidated.