Jun 6 20:21:36 ubuntu ubiquity: grub-install: error: cannot open `/boot/efi/EFI/ubuntu/shimx64.efi': Input/output error.
Jun 6 20:21:36 ubuntu kernel: [ 921.974168] FAT-fs (sda1): Corrupted directory (i_pos 133127)
It wasn't so corrupt that it couldn't be read, but enough that a new file could not be written.
The EFI version of grub completely ignores the destination argument. You can tell it to install to /usr/bin and it it will work just fine, provided that it can write to /boot/EFI.
No, it didn't. From your syslog:
Jun 6 20:21:36 ubuntu ubiquity: grub-install: error: cannot open `/boot/ efi/EFI/ ubuntu/ shimx64. efi': Input/output error.
Jun 6 20:21:36 ubuntu kernel: [ 921.974168] FAT-fs (sda1): Corrupted directory (i_pos 133127)
It wasn't so corrupt that it couldn't be read, but enough that a new file could not be written.
The EFI version of grub completely ignores the destination argument. You can tell it to install to /usr/bin and it it will work just fine, provided that it can write to /boot/EFI.