[Mimedefang] multiplexor errors (ERR Filter timed out)

[Yeager]

I've been running mimedefang-2.1 for a while without problems, and yesterday
the following started showing up in the logs:

Jan 16 08:04:40 mail mimedefang-multiplexor: Reap: Idle slave 0 (pid 9863)
exited normally with status 255 (SLAVE DIED UNEXPECTEDLY)
Jan 16 08:04:41 mail mimedefang[10082]: Error from multiplexor: ERR Filter
timed out

Any Ideas? Machine is Redhat 7.2 with Sendmail 8.11.6