I'm having the same problem, though it seems to be only when I try to reply from an email address that has an image in the signature. It's really annoying since I have multiple work emails with different signatures that I need, and I don't want to have to delete them and paste them in manually each time.
I tried to delete my plist file, but it's not there for some reason:
Image
(yes, I'm in my user library).
Help?
Exact same problem here and defo in my users library. Sigs not working or showing up in preferences. cant write text in main body of message