Linux510 shows in update-grub system only boots to 59

Desktop KDE system- testing branch. Installed linux510 kernel. update-grub shows linux510 during the process but from the top entry in grub, will only boot to 59. Reinstalled grub and another update-grub- Same results. Even with update grub and reinstall, linux510 doesnt show up anywhere in the grub menu on boot. What gives with this?

Found the problem from a janked up UEFI Grub install on a stable iteration on the same machine. Reinstalled GRUB after correcting an error in /etc/fstab. All works. Resolved.