I think this might have been a networking problem! The move to another switch and a good cable, and everything appears to be OK. That would explain the weird, extended, ping times and why there was nothing in the logs. A full SNAPRAID SYNC job went fine. (About 3 hours.)
S'funny I think I remember somewhere in this thread about a 'wind tunnel' using cardboard and duck tape
Raid is not a backup! Would you go skydiving without a parachute?