First of all, I'd like to thank all of your for the information reported. As commented in different forum questions and discussion, the mailbox seems to have some chewing gum these days as you noticed, we are aware of a glitch in the mechanism used for sending and receiving lives.
This occurs when sending or receiving a life in-game, but can happen in more than one stage.
The Studio is investigating this thoroughly and they are working on the fix. Stay tuned guys, I'll keep you posted.
Thank you for your patience and understanding.
It looks like you're new here. If you want to get involved, click one of these buttons!