This is part of the whole "you are no longer allowed to have 2 of the same ingredient on a recipe" update and "you are no longer allowed to have 2 of the same product on a recipe" issue that is fixed in later versions.
Bob's library (and therefore all of bob's mods) checks to see if an ingredient exists on a recipe before adding it, and if it does it increases the count, rather than adding it again.
Since Py isn't using my library, he would need to make this check himself, which is obviously isn't if it is causing this error. (Unless it's during the products error phase, in which case this should fix itself if you update to latest factorio)
