Help request: cu hangs on termination

[Geoffrey Leach]

I'm running AT&T UNIX release 3.2.1 on a generic 386AT.
Occasionally, when I end a cu session (after the connection
is terminated normally) the child process will hang in the
<defunct> stage.  (Modem is a TrailBlazer).  Terminating
the window in which the cu was run does not kill the zombie,
and, of course, the parent hangs around as well.  I have to
reboot to get the port back.  Any ideas?