Apple Mail Send Later function not working properly

Apple Mail has a bug with the Send Later feature - scheduled emails don't go to the Sent folder even it is sent, and it keeps resending randomly, They should move to Sent folder with the thread. How to resolve that error or a problem

I have reset the entire Mail. but doesn't seems resolving.

I have removed preferences. but doesn't seems to resolve.

the attached photo still shows will be sent today. However it has been sent and received at my account. i have contacted Apple but no one was able to help me out with that issue. neither on the This Discussion.. and previous.