How can I repair a file vault disk in El Capitan?

I had to force shutdown my Macbook recently and so I opened Disk Utility to see if everything was okay. I'm running up-to-date El Capitan with a FileVault encrypted drive. Mid 2014 Macbook Pro purchased February 2015.

Running "First Aid" on the outer Apple SSD item appears to be okay. It's when I run "First Aid" with Macintosh HD highlighted tells me that something is wrong and that it needs to be repaired, but there is no repair button. Subsequent runs of "First Aid" keep showing that there's an issue, so it doesn't appear to be repairing during First Aid.

I tried booting with Command + R to repair the disk but it would only let me apply "First Aid" to the Apple SSD, not the Macintosh HD. It said Macintosh HD was not mounted. I imagine that's because it's encrypted with FileVault but I couldn't find how to tell it to decrypt or mount the drive to take a look at it.

How can I run a repair on the disk? Should I even bother?

Thanks!