Normally, this message comes when the OS cannot talk to a disk. But since you had this problem reported to another disk and now that's okay, it would be confusing. To troubleshoot I would check these:
1) If both problem reported disks are on the same controller, I would check the disk controller, it's termination, connectivity etc.
2) Run STM and dd to check each disks and see if it reports any error.
3) If the disks are very old, suspect both disks are bad and replace it.
4) Some of the old disks, might give you error after a reboot and may be another reboot will erase the problem. But this problem might come again after another reboot, so I would replace any disks (if disk is the problem) that ever gave a h/w error.
5) Doing vgcfgrestore should be the task after replacing the disk. You need to recreate the FS and restore data from backup.
6) Check disks and controllers with STM, diskinfo, dd, ioscan -fnC disk etc.
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