unattended-upgrade CPU 100% for 4 hours (every time) [in case of many routing tables]
Consider turning off unattended upgrades in APT. Disable it by doing a grep -R Unattended /etc/apt and looking for:
APT::Periodic::Unattended-Upgrade "1";
Then, change the 1 to a 0. You can try to restart the unattended-upgrade service, but sometimes it's actually faster to just reboot the whole machine.