Set default TTL 64 for tunnels
1.2-x has default ttl 255
vyos@r2-lts# set interfaces tunnel tun0 parameters ip ttl Possible completions: <0-255> Time to live (default 255)
1.4 has default ttl inherit
vyos@r1-roll# set interfaces tunnel tun0 parameters ip ttl Possible completions: 0 Inherit - copy value from original IP header 1-255 Time to Live
Inherit works not properly. So bgp and ospf protocols can't communicate with inheriting.
Also after an update from 1.2 to 1.3/1.4 the cause a bgp session not established.
https://forum.vyos.io/t/ospf-via-gre-tunnel/
https://forum.vyos.io/t/bgp-sessions-with-non-mikrotik-devices-not-coming-up/
https://forum.vyos.io/t/problem-with-ospf-over-gre-tunnel-with-1-3-and-1-4/
https://forum.vyos.io/t/bgp-state-connect-error-via-gre-tunnel/
And others topics.