Nexus 7 MultiROM problem while starting Ubuntu Desktop

Hello Community,
When i try to start the Ubuntu Desktop OS for Nexus 7 i get the following error:

Code:

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mount: mounting /dev/mmcblk0p9 on /root failed: No such device

Could not mount the partition /dev/mmcblk0p9.
This could also happen if the file system is not clean because of an operating system crash, an interrupted boot process, an improper shutdown, or unplugging of a removeable device without first unmounting or ejecting it. (filesystem = f2fs, error code = 255)

BusyBox v1.20.2 (Ubunti 1:1.20.0-8ubuntu1) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs) _

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The file system is according to TWRP ext4.
Any ideas what i could do to get this working?

Regards,
FunnyItsElmo