vlan-ccc l2circuit from double tagged interface to double tagged interface

Hello all,

I've been doing MPLS, LDP, OSPF and BGP for a while now and have been succesfully deploying l2circuits.

The version we're using is vlan-ccc encapsulated interfaces with a single VLAN tag and connect this to a neighbor with similar config. 

Like below:

unit 1187 {
    encapsulation vlan-ccc;
    vlan-id 1187;
    input-vlan-map {
        swap;
        vlan-id 1;
    }
    output-vlan-map swap;
    family ccc {
        mtu 1520;
    }
}
protocols {
    l2circuit {
      neighbor x.x.x.x {
          interface xe-0/0/3.1187 {
              end-interface {
                  interface ge-1/0/9.3708;
              }
          }
       }
    }
}

This works fine. 

But since a while, we connected to a party who wants both sides of the l2circuit to be double tagged.

We tried the following, but failed to make a working connection for the customer.

A side:

unit 1170 {
    encapsulation vlan-ccc;
    vlan-tags outer 0x8100.1170 inner 0x8100.603;
    family ccc {
        mtu 1530;
    }
}     

protocols {
    l2circuit {
        neighbor x.x.x.x {
            interface xe-0/0/3.1170 {
                virtual-circuit-id 1170;
                mtu 1530;
            }
        }
     }
}

B side:

 unit 10603 {
    description "FROM: KPN WEAS core-nkh-03.xe-0/0/3:1170";
    encapsulation vlan-ccc;
    vlan-tags outer 0x8100.603 inner 0x8100.603;
    family ccc {
        mtu 1530;
    }
}
protocols {
    l2circuit {
         neighbor y.y.y.y {
              interface xe-0/0/1.10603 {
                    virtual-circuit-id 1170;
                    mtu 1530;
              }
           }
     }
}

MPLS, OSPF, LDP, BGP all work, and even the l2circuit connection came up. But the customer reported a non working connection. They couldn't sent any traffic over the circuit.

What am I missing here? Do i need to do something with VLAN swapping?

Thanks in advance!

Beeelze