Custom Grub install menu entries truncated

[UncleT]

Based upon the procedure at https://wiki.debian.org/RepackBootableISO I am trying to make some custom bootable ISOs that have multiple options for preseeding.

I've got menu entries like this in a .cfg file in the /boot/grub directory of the custom installation ISO:
menuentry 'Graphical automated install - testvm-gui.cfg' {
set background_color=black
linux /install.amd/vmlinuz auto=true priority=critical vga=788 file=/cdrom/unclet-preseed/testvm-gui.cfg --- quiet
initrd /install.amd/gtk/initrd.gz
}
However, when I boot this image on a UEFI amd64 machine, the menuentry titles are truncated, even though there is plenty of screen space available.

I don't have this problem on amd64 BIOS machines or on arm64 machines.

How do I fix this?

[mrmazda]

On all my PCs I disable graphical Grub boot, and the menus use the entire screen. IIRC, it is GRUB_TERMINAL="console" that disables.