Press E at the GRUB menu. Find the line saying save_env recordfail and delete all «- this was not needed
Only these steps:
sudo -i
Then, run each command, one-by-one.
cd /boot/grub rm grubenv grub-editenv grubenv create grub-editenv grubenv set default=0 grub-editenv grubenv list update-grub
Nor anything after these commands. Simply reboot and it should be fixed.