Bad Timing - S4-E22
Continuity mistake: When John's at Serenity Base, in the shots from inside the pod when Aeryn looks out the window John's standing beside the flag and their long shadows are cast behind them as he looks toward Earth, but when John's on the phone with Jack, in the overhead shots the shadows are being cast in front of him.
Bringing Home the Beacon - S4-E16
Visible crew/equipment: After Rygel tells Noranti that she paid too much for having Moya's modulator fixed, and then begs her to cook for him, Aeryn and John come into view, and as they walk toward the camera we can see the moving shadows of the cameraman, camera, and boom mic at the right side of the screen.
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 ★