Placing an awkward potion in the bottom slot and a pufferfish in the top results in a water bottle rather than a potion of water breathing.

The same happens trying to add redstone to a potion of fire resistance.

The cause might be that the strings are mismatched between obfuscated classes 'acd' and 'acf': "water_breathing" and "long_fire_refistance" versus "breathing_water" and "long_fire_resistance".