I have a late-2013 Retina Macbook Pro running Sierra 10.12.5 with a myriad of issues that I've been trying to work out. Today's problem: First Aid says there are problems with the partition map that might prevent booting, and to fix them, I need to run First Aid from Recovery. Easy enough.
So I boot into Recovery and run First Aid and get the same message: run First Aid from Recovery, even though I'm already in Recovery. I get the same message in Internet Recovery and when running Disk Utility off an external macOS installer USB. How can I get First Aid to run in Recovery?