Finally got off my ass and booted up my save again. Going through and knocking out absolutely everything possible before ending chapter 2, and while you don't have to 100% everything, it is damn close. Some mini-games barely require any work (bowling, batting cages, arcade games) and some require 100% or damn near (crane games, disco). I'm just glad equipment is the about the only thing item wise that's tracked specifically and that RC parts have their own completely seperate inventory, because I am getting hit with the item corruption bug so frequently that it's become it's own unique challenge for me to overcome out of sheer spite.
It only effects inventory items, so anything registered to RC parts, Equipment (it'll corrupt but restore just fine after a save) or thrown in my item box is safe, but any consumable/sellable is liable to be destroyed anytime I activate a side/story event or eat. Sometimes saving will revert it back to what it originally was, other times it can change it into something different, which can even be something isn't supposed to be in your consumable inventory (an RC Gear for example). When this happens, trying to put it in the item box will put a broken version in it (and keep it in your inventory) that does not stack and can be put in infinitely. Trying to withdraw the broken item keeps it in the box AND corrupts whatever empty space it now takes up in the same way as the previous. The only way to get these out of your consumable inventory and get your slots back is to fill up your inventory, then find a Dream Wheel or someone being harassed by some thugs and push the corrupt item to your item box when you get your reward. You can't just pawn off the corrupt items either, since they're never meant to be in your consumable inventory, the storekeeper doesn't even show them on his list of sellables.
Or save editing. But at that point, I might as well just run an achievement unlocker. It's technically a "game breaking" bug, but not so much so that I can't work around it within the game itself. Hell, by the time I'm at 80% I'll probably understand it enough to abuse it somehow, there does seem to be some pattern to it.