Question: Mail—Reply/Reply-all window hangs
I've just upgraded to High Sierra, and now whenever I command-R or command-shift-R to reply to a mail, the composing window opens, it allows me to add addresses and even a subject, but it won't let me write in the compose window UNTIL I quit Mail and then reopen it. When I reopen Mail, the compose window I originally couldn't write in is there, with all the addresses and subjects I originally added, and works perfectly fine. This happens every time I cmd-r/cmd-shift-r; the same thing happens if I use the pull-down Message menu.
I'm currently using macOS High Sierra 10.13.1 and Mail 11.1 (3445.4.7).
Any help will be much appreciated, as I'm sick of having to quit Mail whenever I have to reply or reply-all to an email (which is about 8–10 times an hour!).