Corrupted /boot/grub/grub.cfg with 2 UEFI boot directories

[UlfZibis]

I have 2 Ubuntu 64-Bit installations on 2 different partitions.
After booting into the 2nd installation, I have changed in /etc/default/grub:
GRUB_DISTRIBUTOR="Ubuntu-64"
After grub-install and update-grub I got new .efi files in /boot/efi/EFI/ubuntu-64 and a new /boot/grub/grub.cfg and /boot/efi/EFI/ubuntu-64/grub.cfg refers to the partition of the 2nd installation.

Now /boot/grub/grub.cfg of the 2nd installation is corrupted (see attached grub_2.cfg):
- There are some entries like:
  menuentry 'Ubuntu 16.04.1 LTS (16.04) (auf /dev/sda8) (auf /dev/sda5)'
- Some of them don't define initrd.

I tried again after deleting /boot/grub/grub.cfg in the 1st installation and got another corrupted one with similar errors (see attached grub_1.cfg).

After booting into the 1st installation with update-grub I got similar errors (see attached grub_3.cfg):
- There are some entries like:
  menuentry 'Ubuntu 16.04.1 LTS (16.04) (auf /dev/sda8) (auf /dev/sda5) (auf /dev/sda8)'
- Some of them don't define initrd.

I also see, that the localization in grub.cfg is not consistent. In some menu entries "with" is translated to german "mit", but not in all.