Not really a bug but a consistency error.

I accidentally clicked twice on the button to claim Melody's Cottage prize and noticed that the text says that you've already claimed the advent calendar prize for today.

I know it's not been called "advent calendar" for like a decade now so I found it very weird.

I think double clicking is the only way to access that error message, since returning to the MC page after claiming the prize replaces the link with the Donate 2,000 sP link.

I'm on Windows 10 and using Chrome, but I don't think that's really relevant here lol.