Dell XPS 9550: cannot boot Ubuntu from NVME

Hi,

I cannot boot ubuntu from nvme disk event though sata ssd works fine. System just tells boot failed and then opens dell's boot assistant and starts scanning system for errors and finds nothing.

Install went without any problems, disk was found and I was able to setup partitions and install system and grub.

Tried booting in legacy mode - no luck.

Tried anything I could think of, but the result is the same.

Any ideas?


Ubuntu Gnome 17.04 (also tried Ubuntu 17.04, 16.10)
Bios: latest (1.2.25), tried two versions before that.
NVME disk: Samsung 960 PRO 512Gb.
Sata ssd: Samsung 850 EVO
Boot mode: UEFI.
Secure boot: disabled.
SATA mode: AHCI.