I don't think it because of the music or the version of warcraft. I try turn off all music option in ver 1.24e, and then upgrade to 1.25b but the death bugs still occur randomly. But it's only happen from chapter 4 (I'm not sure because I make through first 3 chapters without die a time).
I think one possible reason is that your campaign doesn't synchronize between chapters. Why I can say this? Because chapter 1,2,3 link to each other very well, elite and epic boss progress bring to the following chapter. But since chapter 4 everything went wrong.. In chapter 5, the
**** mode doesn't apply anymore. And then in chapter 6, I can see the mark at Elite and Epic bosses in chapter 4... Maybe you already solved the death bug, but it doesn't apply to all map... That's what I think.