Comment # 2 on bug 996841 from Emilio Recio

So, I changed the crypttab to use UUID= instead of /dev/..., updated the
timeout=30,luks,discard option too rebooted... nothing.

So, I changed the boot params ("E" at grub menu) and added "insmod dm_crypt"
"insmod dm_mod" to the params, it said the modules weren't found, and then the
screen went grey, and in the middle it asked me for a password!! I typed in the
password, and everything worked as normal.

I repeated the above, and this time it was SNAFU. Just hung there.

Shutdown completely, and rebooted, without changing any settings, and back to
Situation Normal AFU... it just hung there with a blank screen.

I rebooted again, without changing any settings, and this time, I just let it
sit there ... and the timeout kicked off, and booted.

Did nothing, rebooted immediately, and I got the grey screen with green text to
ask for a password!! WTF??

I went into CTRL-ALT-F2 to check if the drive was mounted, and it was! So I did
another reboot from the command line. Worked again!! And everything was
mounted.

Now it works most times... is there something in grub/systemd that updates the
boot options/drivers/etc?

Sounds like a video card or hardware driver issue - none of it is consistent??
In previous versions of the kernel there were issues with the Skylake hardware
in this machine. Perhaps this is a coincidence with enabling encryption and
really the kernel (4.7.0-2-default) is still a bit buggy? For example, during
boot, instead of the tumbleweed animated screen (after kernel loads) I just get
three tiny question marks with green background. But on shutdown, I get the
tumbleweed animated screen (most times).