Just an FYI, I've just realized that ad blockers can easily block the signatures my users create. We'd been looking for the culprit in the disappearing sig's, and were getting weird results, with some browsers displaying them and some not, but it wasn't consistent. Finally it dawned on my that I have AdBlocker running on both Chrome and Edge, and when I paused it the sig's came back.
So now I advise all users to disable their ad blockers on my forum, and all seems well. And I wonder what other problems those things are causing? Anyone know?