...Different Destinations - S3-E5
Other mistake: While in the past on the Jocacean Memorial Planet, after Dacon is sent up on the wall by his commander, when the Venek Horde are coming over the wall Aeryn pulls one down and throws him to the ground, and we can see one of the armor pieces lying on the ground with the actor name "Dacon" written on the inside in English.
Other mistake: In this episode the family that John and the gang encounter are able to understand him. Yet if the planet has never experienced encounters with alien life forms, this is impossible without translator microbes.
Chosen answer: It's never explained. John mentions a theory that his less technologically developed craft simply interferes with the wormhole less than the "superior" Vipers, but they never make a concrete determination on that point. But we also have to take into account the fact that Moya traverses wormholes with no ill effect as well.
Garlonuss