ALM serial ports hang?

[Rich Baughman -CFI-]

We are running SunOS 4.0.3 on our Sun3/180 and Sun3/280 file servers.
Since our conversion to 4.0.3 two months ago, it seems the file servers'
ALM (16-port serial port multiplexor) hangs itself periodically, requiring
a reboot.  In particular, it happens to the 3/280 once or twice a week.
Both servers are running kernals with the serial port patches from Sun.
Does anyone have any ideas as to what we might do to avoid this?  Is there
a hardware upgrade that fixes the problem?  I'm still waiting for the Sun
Answer Line to respond to my call.  (No, I'm not holding my breath :-}

[[Ed's Note: v8n172 talks about a fix for hung ALM-2 boards. Basically, to
recap the problem was in an older revision CPU board. I'm not sure if this
is the same problem, or something induced by the upgrade to 4.0.3,
though. -bdg]]