>If my fix is right, you'll see something like "ERR_add_error_vdata: Verify error:" and the verification will continue.
Yes, that's exactly what happens. There are several "ERR_add_error_vdata:"
line, including the "Verify error". Then it repeats (probably checking another
certificate. Then I get "Welcome to grub" and the boot menu.
And then the "ERR_add_*" lines repeat again (probably checking the kernel
signature). And then it boots.