18404 xwp      NAMI  "/emul/ibcs2/tmp/wpc-weaver.t/excmsg60"
    18404 xwp      NAMI  "/tmp/wpc-weaver.t/excmsg60"
    18404 xwp      RET   open -1 errno 6 Device not configured

This is not a bug.  If you open a FIFO for writing with O_NONBLOCK
(essentially the same as the old O_NDELAY) and there are no readers,
you get ENXIO.  This is also how it's defined in SVID, and it's what
SCO does.

The problem lies somewhere else, probably in the waitsys() emulation.