I believe your efi system partition is corrupt. You could confirm this by checking /var/log/syslog for more detailed errors at the time this happened, and can fix it by unmounting it and running dosfsck on it. Please let us know how this goes.
** Changed in: grub2 (Ubuntu) Status: Confirmed => Incomplete -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1526608 Title: package grub-efi-amd64 2.02~beta2-9ubuntu1.6 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1 - on macbook pro To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1526608/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs