The network configuration is not working on a droplet after reboot

For some reason when I reboot my droplet, the network configuration is not working. The details appear correctly for the interfaces file, but the interface doesn’t appear to be getting assigned.

To fix that issue I have to do this:

ip address add IP_ADDRESS_1/20 dev eth0

That updates the output of ip addr to show that the IP address is assigned, but connectivity still will not work until the route is setup.

ip route add default via IP_ADDRESS_2 dev eth0

This updates the ip route output to have a default route.

If I reboot the droplet I can’t connect to the droplet via SSH (any attempt to access the public IP address fail) and I have to use the web browser console to access the droplet and to use the commands above in order to restore the correct work of the server.

Can anyone help me to find out the reason which may cause this issues?

Every time when I reboot I reproduce the same issue. Any suggestions where I have to look first?

Thanks!