Look at the Princess (2): I Do, I Think - S2-E12
Visible crew/equipment: After John and Princess Katralla escape the room filled with poison gas from the silver orb, it cuts to Rygel and Empress Novia discussing John's need for protection, and we can see the movement of the dark-haired puppeteer behind Rygel's chair.
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 ★