I lost track of how low my energy was, and tried compressing butterfly butter when my energy was very low. The dialog popup said that I turned the butter into cheese, but there's no cheese in my inventory. The butter was still in my inventory, though, and when I tried compressing it again, I got an error "A wee problem: Error: (0) can't find the itemstack to work with". I'll try reloading the window and see if that sorts it out.