3489 mouse issue

Recently, I had "Saturn," our D02, up to research a support question
yesterday, and I noticed that if I clicked the mouse on our "new" 3489
while connected to the D02, it would immediately crash the terminal
session, with a joblog message about a light pen or magnetic stripe reader
problem.

On our old 3487, such issues never came up. Mouse clicks were, for the
most part, just ignored.

Is there any setting I can change in either the terminal itself or the
*DEVD, to suppress that, without eliminating mouse usage with any of the
other systems this terminal can be patched into?

Or do I just need to put up a sign: "Don't click the mouse when connected
to Saturn!"?

--
JHHL

P.S.: We call that box "Saturn" because it's the oldest AS/400 we still
use (as in "Saturn, the Bringer of Old Age").