Reading through the forum, it looks like next step is to check Disk 2 using the "Check File System Status". I stopped the array, put it in maintenance mode and started it again. I used the GUI and ran a check with option "-n". It reported back:
Phase 1 - find and verify superblock...
superblock read failed, offset 2199023247360, size 131072, ag 2, rval -1
fatal error -- Input/output error
I was hoping it would give me more info than that. Don't know what to do from here.
NOTE: I also noticed disk 3 which wasn't having problems before, is now reporting "unmountable disk". Only happens randomly as a I start and stop the array. Sometimes it mounts, sometimes it doesn't. Odd.
nas-diagnostics-20230319-1549.zip