I don't know how many times we can repeat this.
Do not install grub-customizer!!!
It can create very serious problems that will not be cured by simply uninstalling grub-customizer.
It is like the old saying:
It's pretty hard to unscramble scrambled eggs.
Unless you really know what you are doing often the only solution to fixing a severe mess that grub-customizer has created is to do a clean install.
Please do not install grub-optimizer., or you may greatly regret it.