I activated the private networking ip on my droplet (Following the instructions provided by DO. ).
Now that droplet syslog is being spammed with the same error message every 1-2 second.

kernel: [138769.402520] icmp6_send: no reply to icmp error

does someone now where this error is coming from ? and how to fix it?

system and running programs:
debian 8.8
php-fpm 7.2.8
apache 2.4
postfix and dovecot

/etc/network/interfaces

# This file describes the network interfaces available on your
# system and how to activate them. For more information, see
# interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet6 static
        address 2A03:B0C0:0001:00D0:0000:0000:18E4:B001
        netmask 64
        gateway 2A03:B0C0:0001:00D0:0000:0000:0000:0001
        autoconf 0
        dns-nameservers 2001:4860:4860::8844 2001:4860:4860::8888 8.8.8.8
iface eth0 inet static
        address 46.101.81.61
        netmask 255.255.240.0
        gateway 46.101.80.1
        up ip addr add 10.16.0.5/16 dev eth0

auto eth1
iface eth1 inet static
        address 10.131.62.249
        netmask 255.255.0.0