https://wiki.unraid.net/Troubleshooting#Re-enable_the_drive
Make sure the emulated disk is mounting and contents look correct before rebuilding on top.
Most likely all files are fine, but unless you have pre-existing checksums or are using btrfs no way to know for sure, you can however rebuild that disk to a spare one then compare the data with the old one.
Disk3 is showing a pending sector, you should run an extended SMART test, disk4 looks OK.
Also need to run a filesystem check on the emulated disks 3 and 4.
Newer kernel can detect previously undetected corruption, you should backup your pool, re-format, then restore the data before or after upgrading back to v6.9