NO EXPERT HERE; However, I saw something similar last night Jan 10, when I let Ubuntu install the latest Ubuntu 16.04 update. So far, no problems.
After updating Grub2, My Terminal
uname -a command yields:
Linux 4.13.0-26-generic #29~16.04.2-Ubuntu SMP Tue Jan 9 22:00:44 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
Guessing 4.13 is installed and your Grub isn't pointing to it. Look for it when booting in the Grub boot menu.
You could start Terminal and List all kernels including the current booted using command:
dpkg --list | grep linux-image
I checked the installation log using Gedit
and found the following line:
upgrade linux-generic-hwe-16.04:amd64 220.127.116.11.44 18.104.22.168.46
indicating the 4.13 upgrade started.
I use "Grub Customizer" to maintain my Grub. Be extremely careful, if you use it. Search for "How to Install Grub Customizer 5.0.5 in Ubuntu 16.04 LTS" . It will install the latest version. Mine is 5.0.6.