Apologies
On further investigating, the problem is not that 2.06-7 does not fix
the problem, but rather that on doing an apt upgrade, the
grub-efi-amd64-signed package remained at 2.06-5 even though other
grub-related packages were updated to 2.06-7:
grub-common/testing,now 2.06-7 amd64 [installed]
grub-efi-amd64/testing,now 2.06-7 amd64 [installed]
grub-efi-amd64-bin/testing,now 2.06-7 amd64 [installed,automatic]
grub-efi-amd64-signed/testing,now 1+2.06+5 amd64 [installed,automatic]
grub2-common/testing,now 2.06-7 amd64 [installed,automatic]
