What Was Lost (1): Sacrifice - S4-E2
Continuity mistake: After Oo-Nii tells John that the old woman stole his gun to kill Vella, John looks down at his holster and finds Winona gone. Later while he's shouting for Granny, it keeps cutting to the old woman while she's holding Winona, and after she whispers, "Receive the spirit," it cuts to John and Winona can be seen in the holster on John's leg, but in the next shot Granny still has it.
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 ★