I have a customer with 6 x440's and 1 x460 switches in a stack. The 460 is the master in slot 1. The problem is that the switches on occasion lockup. When this happens all the lights go solid and no traffic will pass. The fix is to reboot the stack. When I have looked in the logs there were no signs of what caused the issue. They were running 220.127.116.11 patch 1-33. I have just upgraded to 18.104.22.168 patch 1-9. I am looking for anyone that has the switch stacks lock up. I have made sure it was not a loop. I have checked that is not an Intel NIC multicast issue.