So I found some kind of bug involving scrapping. I had two writhing tentacles, and scrapped it twice - one at a time - and somehow ended up with 0 being listed in my inventory as 1. I *think* I had also been moving other items around in my inventory immediately before this. Maybe something about this caused it to be left in my inventory as an item when it should have been removed? Specifically, I think I moved slot 7 into slot 5, then slot 2 into slot 5, with the tentacle ending up in slot 6. Then I scrapped the item in slot 7 followed by the tentacle in 6.
Do you remember if you had an Incredibly Poisonous Mushroom on you, at all? I think I've narrowed it down to a problem with that item specifically - when an item swaps positions with it, bad things happen.
E: Oh, no, nevermind. Something WAS wrong with that item, but the rot runs a lot deeper. Houuuugh...
EE: AHA. Well! Turns out I'm a bimbo. So, if you want the Sausage Factory Behind The Scenes:
Basically, when a Consumable item is swapped, I added in some extra code to handle applying the Stack for that both items onto their new destinations. HOWEVER!... this was only ever one way. I somehow never noticed that when you swap two consumable items, the result is that the item that performs the swap is fine, but the item that gets swapped as collatoral gets its stack replaced by the item it was swapped with.
ie: You have 4 Cores and 8 Paravines. You swap Core right. You now have 4 Cores and 4 Paravines, and the Paravine's variables are very confused by this.
I'm gunna need to make some minor additions but it should be fine. Thanks for the report! It'll be fixed by 1.0.7.