Well that's weird. When you set a new Event Handler it should destroy any previous one that was set. Is it possible that the problem sequences were duplicated from other sequences that had a Game Started event handler? That's a separate code path and it's possible there's a bug there. Any chance you could send me a project that replicates the issue?
I just fixed it by copying and pasting command lists from the offending sequences into new clean ones with new names and linking them up as they were. Changing the names back to the way they were doesn't cause the duplicate starts again, though. Does that suggest there is some reference to the name of the sequence being retained where it shouldn't be?
That's what it sounds like alright. If you have time, it would be great if you could figure out a sequence of steps that reliably causes the issue. I'll take a look at it myself this week.