Situation:
A city completes a cargo ship and tries to quickly setup a trade route with a CS when a barbarian ship is nearby.
Result:
The trade route is immediately pillaged and a clone of the barbarian has now appeared.
This can be repeated as many times as you complete a cargo ship, late-game this can be every turn.
I have never seen this with land-routes or in the early, mid game.
There is no camp nearby, it is many tiles away on an island.
Situation: A city completes a cargo ship and tries to quickly setup a trade route with a CS when a barbarian ship is nearby.
Result: The trade route is immediately pillaged and a clone of the barbarian has now appeared. This can be repeated as many times as you complete a cargo ship, late-game this can be every turn.
I have never seen this with land-routes or in the early, mid game. There is no camp nearby, it is many tiles away on an island.