Reply with history sending mail twice 6.5.4

We are trying to upgrade our mail template from 6.5.1 to 6.5.4. During testing of 6.5.4 template we found out whenever a user is replying with history or replying to all with history, it sends the email and then it prompts with this msg.

“Are you sure? this message was already sent to one or more recipients. If you send it again, some recipients may receive more than on copy of the message. Select Yes to continue, No to cancel sending.”

if you say Yes it sends another copy, if No it stops but puts you back in the email which you are trying to send.

I tried to go through debug mode and it looks like its looping again after sending the email. This is happing to 3 people i have tested with.

Does anyone has a clue why this is happening. It does not happen in 6.5.1 template.