Thanks for playing our game and the feedback! The video actually helped us see exactly what was going on as well as likely with others - the hitbox for where you put the feathers seems to be a bit small based on feedback. There's a different sound effect for when you drop them and feather particles appear (which doesn't count as a 'stuff') and when you manage to correctly place the feathers inside the object. From your video, it seems like you didn't get enough 'correctly' placed to trigger the next part of the game - three feathers will trigger the button to appear.
If you see the feathers drop, it's not placed properly and makes a more of a "fwoosh" sound. From the video, it seems you're going a bit too low into the item, this is something we're going to fix after the jam voting period. The target area is RIGHT at the opening of the item, as well as slightly below it. We've seen multiple people go too far inside the item or drop too high above.
Thank you for your review and rating! We really appreciate it and it makes us happy to see people enjoying, despite the hitbox placement choices causing some trouble!