EXT4 is considered reliable and Ubuntu defaults will have formatted the drives appropriately for normal use like LE, and while Kodi crashes can corrupt files in the filesystem, esp. databases which Kodi is responsible for managing, they should not cause corruption to the filesystem itself. This means filesystem errors in the system log are more likely to be the result of power issues, i.e. sudden power loss, or issues with the physical disk media.
If you are lucky it's minor corruption and running fsck against unmounted drives will fix things. If you're less lucky the physical drives are okay but the filesystem is properly messed up and needs a total rebuild. If you're properly unlucky there's physical media damage to the drives. These days physical media damage is rare unless some form of physical shock is also involved, but it's not completely impossible. Failures also follow a bell curve: if the drive is going to fail it's more likely to be when the drive is still very new, or years later when it's very old. Failure rates often correlate to the manufacturing batch of the drives too, so the ideal scenario when purchasing a set of disks is to acquire disks from a variety of different batches not all drives from the same batch.
The only way to find out is trying to fsck, or trying to reformat and rebuild. Beware that if formatting, the default quick format done by most tools may not find physical media issues. That kind of thing is normally only found by trying to 'zero' the drive by writing to all sectors (also rather long and boring).
