This really saved my ass! Thank you so much. Accidentally updated to 6.2.4-25556 and my synology server did not boot up. I was very sure the bootloader can support it but no idea what was the reason/hiccup for not booting into the system. The tips in this post helped me to revert back to 6.2.3-25426. Phew!
No more updating to the latest version, no more.