CommodoreAlpha

I've already tried adding the item to other tabs (and tried overriding items of different IDs - not that I'd expect it to work, but couldn't hurt to try). I've also tried commenting out parts of my code, but it seems the only way to "solve" the issue is to not add it to the creative tab at all or to not override the item at all (adding non-overriden items, i.e. my own items works just fine). Either there's something quirky about setCreativeTab, addSubstitutionAlias, or me just being a noob - I highly doubt it's anything else.

I'm new to Java (and subsequently Forge modding), and I'm testing out some basic stuff, including overriding vanilla items. The code in question is here. I'm noticing that whenever I call the setCreativeTab method on an overriden item (overriden via addSubstitutionAlias method), it shows up twice in the creative inventory. If I don't call it at all, however, it doesn't show up at all. setCreativeTab works just fine with my own mod items. (Using Forge version 10.13.4.1558 for Minecraft 1.7.10)