Signature versification failure

[Paul]

I normally sign and encrypt emails, but I have found that when signing-only I receive "signature verification failed" for that message. Signed and encrypted messages verify.
My signature has a '--' line in it, but I have also tried adding a space to the end '-- '.
When clicking Send, I see that line being changed to "- --' or '- -- ', before it is sent, so I assume that's the problem.
I'm using TB 17.0.8 and Enigmail 1.5.2, and have tried Enigmail 1.5.1 with the same result.

Preferences - Advanced is check marked, as it always has been:
'--' is a signature separator
Any ideas?

[Paul]

I've been told by someone that gpg is responsible for this behaviour, and not Enigmail, so - sorry to have troubled you.