Harmy said:
Also, I suppose that if, after the muxing's done, I try re-muxing the file and it goes fine, it's safe to assume that the same error didn't occur again, right?
Yeah, once you have it muxed with everything in it, try remuxing it with just the 5.1 DTS soundtrack and see what happens. If all goes well and you can see the cantina scene just fine, everything should be good.