This would certainly not be a bug in grub, which has nothing to do with hibernate/resume handling.
What disk is the target for your hibernation? What are the contents of the RESUME setting in your initramfs? (unmkinitramfs /boot/initrd.img /tmp/initrd; cat /tmp/initrd/main/conf/conf.d/zz-auto-resume)
Resume from hibernation only works if you resume into the same kernel after hibernation that you were running before hibernation. Is it possible that you were rebooting into a different kernel version due to kernel security updates having been applied?
This would certainly not be a bug in grub, which has nothing to do with hibernate/resume handling.
What disk is the target for your hibernation? What are the contents of the RESUME setting in your initramfs? (unmkinitramfs /boot/initrd.img /tmp/initrd; cat /tmp/initrd/ main/conf/ conf.d/ zz-auto- resume)
Resume from hibernation only works if you resume into the same kernel after hibernation that you were running before hibernation. Is it possible that you were rebooting into a different kernel version due to kernel security updates having been applied?