In the Deep Space Nine episode "Whispers" Miles O'Brien is apparently replaced with a replicant that was supposedly programmed to interrupt some peace talks in the Parada system. At the end of the episode, the replicant is shot and killed. But how did Sisko and team know that the O'Brien they went home with was the real one and not a replicant?
According to Bashir:
"There was no way to prove he wasn't you. He passed a physical exam with flying colours, and he sure knew his way around the station."
If they couldn't prove that the replicant wasn't O'Brien, it seems strange that Sisko and the crew would blindly take the Paradan rebels at their word, rather than trust in their own tests and interactions.