That isn’t what wiki says:
However, they unknowingly or unintentionally left the live percussion primer in place at the rear of the cartridge. At some point during filming the revolver was apparently discharged with one of these improperly-deactivated cartridges in the chamber, setting off the primer with enough force to drive the bullet partway into the barrel, where it became stuck (a condition known as a squib load). The prop crew either failed to notice this or failed to recognize the significance of this issue.[/quote]
Furthermore I have NEVER heard of a primer going bang twice. I don’t think it is even possible. If this was possible, I don’t think they would reload ammo they way they do, which includes shoving a metal rod to push out the primer. If it were live you run the risk of it going off.
However if they DID do it how you said they did, it IS possible that it didn’t go bang the first time. A light strike or a hard primer or a faulty primer may make it not go bang the first time, but will go bang the 2nd time. Rimfires are notorious for that, though it is much rarer on centerfire cartridges.