After last update using the "discover"-application:

# ls -l *vm*
lrwxrwxrwx 1 root root 29 Feb 20 12:53 vmlinuz -> boot/vmlinuz-4.4.0-63-generic
lrwxrwxrwx 1 root root 29 Feb 17 16:24 vmlinuz.old -> boot/vmlinuz-4.8.0-36-generic

As You can see: Back from 4.8 to 4.4!!! That's totally wrong.

After checking the configuration and rebooting,
the result is:

GRUB still boots 4.8-hwe-kernel correctly!

I close this topic.