If my understanding is correct, when the traffic egress out the port where "cep cvid" is configured, you would want the switch to include the CVID to the traffic and send it out the switch.
Which means VMAN double tag gets removed but will have the original TAG value and you would want to translate the original tag to CVID on the untag egress port.
If so, this configuration is required "configure vman add ports cep cvid translate '.