Ok, with a compliant EFI implementation, there's no reason that warm vs cold boot should be a factor either, but it's interesting to know and gives us a starting point.
If you've hit the problem so many times already, it seems likely that the problem will reproducible again on updates to the grub2-signed or shim-signed packages on your system. You may even be able to reproduce it manually by running 'efibootmgr' commands. Any reproducer that gets us some dmesg output would be helpful.
Ok, with a compliant EFI implementation, there's no reason that warm vs cold boot should be a factor either, but it's interesting to know and gives us a starting point.
If you've hit the problem so many times already, it seems likely that the problem will reproducible again on updates to the grub2-signed or shim-signed packages on your system. You may even be able to reproduce it manually by running 'efibootmgr' commands. Any reproducer that gets us some dmesg output would be helpful.