Boot device selected in BIOS being ignored


I puchased a LarkBox Pro and an SSD M2 480Gb drive in which I installed Ubuntu.

In BIOS Boot drive selection I put FIRST “ubuntu” drive and second the Windows (eMMC) one.

In cold boot ALWAYS boot Windows, ignoring the “ubuntu” preference

In warm boot (reboot from Ubuntu, forced manually to boot in start) sometimes boot Ubuntu (M,2, as configured in BIOS) and sometimes Windows (eMMC second option in BIOS).

I mean it boots from eMMC and NOT M.2 as selected. Grub contains both Ubuntu and Windows entries. But not booting GRUB, booting from eMMC.

Is there something i’m missing?