AC3 and Ogg in one OGM

[Queyalus]

I just tried encoding a OGM ogm in which the first audio stream (the more important one) is left as ac3 (for the better quality) and the second one (the additional one) converted to ogg (to smallen the size). Everything went ok, but when I try to play the file in BS, I only hear the Ogg-Stream, because the other one is way too low.
Starting the file, both audio streams are checked, and when I check one, it looks normal, but both streams are still audible, so I can't swap to one of them. I first thought I misencoded, but playing with Zoom works well, I can swap perfectly and both sound perfectly normal, so I guess it is a bug of BS, ain't it? btw, I use 86 Build 499