Me either. I have an Asus with my Intel in it and it has CSM and secure boot can be disabled and fast boot. If we have the exact board model can look it up.
It is an ASUS PRIME B250-A motherboard
Now I got these messages: 
And :
I think you need to disable secure boot by going into advance settings and you will see where you can delete the existing keys from secure boot. This will then disable it and you just have to save the settings when exiting the uefi screen. You should see the secure boot is on in that screen. Once you delete or erase the keys it should show secure boot is disabled, Then save the bios setting when exiting.
I realize that what is being damaged is GRUB, I have just recovered it with some indications that I found on the web, but this is why it is happening, they already go several times, it will be because the secureboot is activated or it could be another thing?