I have the same bug in Kubuntu 64bits. I have solved it changing the style of the widget of gtk+ by a moment when i run the Grub Customizer. The style I have is "oxygen-gtk+", I change it by "Clearlooks" (for example) and works.
I have the same bug in Kubuntu 64bits. I have solved it changing the style of the widget of gtk+ by a moment when i run the Grub Customizer. The style I have is "oxygen-gtk+", I change it by "Clearlooks" (for example) and works.