Reply Email replaces original message with old one

I have the Key2 with the latest beta Hub.
Today I sent a reply all using my exchange email on the Key2 and the recipients received the body of an old, unrelated email - complete with the original images under the correct address headers.

Has anyone experienced anything like this before?

Thanks

it seems to only happen with one account, only on replies and only when email sent from the main hub using the drop-down to select the email address. when sent from that email address directly there are no issues.