Both disks getting disabled at the same time suggests a connection/controller issue, I would start by upgrading the firmware on both HBAs, especially the second one which is very old, and it's where both disabled disks are connected, both disabled disks likely also share a miniSAS cable, so you can also swap/replace that to rule it out, after that and since disk9 is mounting correctly you can rebuild on top and re-sync parity, you can do both at the same time, if it happens again it would be important top see the syslog.