trouble with utf-8 vbell_msg

MANY years ago I had vbell working with a Japanese message.
Recently I tried to get it to work again, but not having much luck.
If vbell_msg is in plain ascii, vbell works fine.  If I enter a utf-8
message, I do get a vbell message in the status line, but the characters
are garbled, i.e., strange nonsensical characters.  If I add "defencoding UTF-8"
I don't get a message at all: the whole screen flashes instead
(similarly to what
vi does when there's a faulty keystroke).

Thoughts, hints?  Thanks much.

Henry