I harvested from a Simple Compost Bin for the first time when it showed the green check mark, then quickly stepped aside and pressed E to open a Cardboard Box next to it. The game froze, allowing me to notice that the "+ New Item" notification showed 200 Iron rather than the expected amount (something less than 200, turned out to be 9) or item (Organic Quick Grow Fertilizer). Additionally, the quickbar showed that the first slot in my previously empty Backpack was occupied by 12 of an item I don't recognize (some kind of dish I haven't unlocked, I'd guess).

The game stayed frozen on that screen for 1-2 minutes, then resumed running at normal speed, opening the Cardboard Box I'd activated before the freeze. My inventory then correctly showed 9 Organic Quick Grow Fertilizer, rather than the 200 Iron or 12 of the unknown item.