Hi Tynan Elder Oak,
they are not stuck, they are waiting to be read.
When you write a PM, it sits in the outbox until it is read by the recipient. It then moves by itself into the "Sent messages" folder.
Don't ask me why
It's just how the board software (phpBB3) works.
I don't think anybody ever died thinking they loved people too much, or had too much joy, or made too much music.
(If the post above is written in green, I'm posting as a moderator. If not, then I'm not.)