Comment 8 for bug 1806813

these 3 b+ issues you refer to were with the 4.4 kernel in 16.04 (bugs in the interaction with backported patches of the NIC driver)

... the above 18.04 should use a newer kernel (4.15 ?) which should have the necessary patches included already, this looks more like the netplan configuration was not done correctly during install ... (check /etc/netplan/ for a yaml file and take a look at https://netplan.io/ for info about how to set up its contents)