I'm getting this message when I try to run first aid on the 2tb fusion drive in my 2016 27in iMac: 'THere is not enough free space in the Core Storage Logical Volume Group for this operation'. THere's 900GB+ free on the drive itself - I can't repair the drive, even if I reboot into recovery. Anything online that looks like a fix involves wiping the drive and setting it up again. I have backups but I'd obviously rather not have to go through all that. Any ideas?