Traefik proxy to another Traefik server

I have two servers: server1 and server2
server1 is visible on internet (cloud hosted)
server2 is internal connected via openvpn to server1

both have traefik installed. in server2 there is a service on port 8069, w/c is also proxied by traefik on port 80.

So below works:
client -> server1 -> server2 (port 8069)
bypass traefik on server2

but below return 404 not found
client -> server1 -> server2 (port 80)

Note: If I curl or wget to server2 port 80, it does not 404.