Grub settings and options
Default kernel parameters: "quiet splash".
In my opinion you will get more sucessful boots and reduced graphical errors on boot if you remove quit and splash. Specifically the splash screen can make strange things happen and when removing "quiet" you are able to debug if there is an error.
I also tried to fiddel with "/etc/grub.d/48_linux_zfs" where I tried to out comment #vt_handoff="1" and set quiet boot to zero: