I can edit the original message as if it were mine.. My signature and the
reply headers don't appear. Tried repair (followed by restart) and also
reinstalled Office (followed by restart). Nothing seems to fix the issue.

Also a more annoying Outlook crash whenever I send a reply. It almost
always crashes and restarts after a reply is sent.

Further , I cannot select anything from the drop-downs as they close
instantly (like a GIF).. Let me know if you have any clues.