Do a verbose boot so we can see when CAM starts its probes.
It is probably the SYM driver rejecting the initial bus scan
from CAM, and then later (after it is too late) notifying CAM that
a new bus and/or devices are present asynchronously.
I'm not sure how easy it will be to fix, the SYM driver is 10,000
lines and it will take a few hours to figure out how it deals
with the SCSI bus scan.
-Matt