I was writing an answer, but I think it is wrong. A question first:
All audios are on audio track 1?
yes they are...
Well, there is no "navigation" being done that is relevant to audio track selected. So I'm going to guess it is a receiver issue.
But if it is, you still have to deal with how to get the program to work right.
a) Create a 5.1 for the one stereo program.
b) You could try the non-playlist "old" way, hoping that specifying a link each time might prompt the receiver? The old way being to link the play all button to video one, end action of video one to video 2, etc. each video to the next. The end action of 1 will specify track 1, (and more importantly, the end of video 2 will specify audio track 1 for thenext video). It should not make any difference, since it is not change, but who knows.
c) It is also possible that the non-playlist linking from video to video will result in correct audio.
Thanks Stan for the suggestions. I did not use a playlist for this. Essentially the "Play all" Linked to movie 1, The end action of movie 1 was movie 2 and so on....
Okay, well that was "c"! I'm stumped. I'm curious as to whether the receiver involved will adjust if the disk has a button for the stereo movie and then a 5.1 movie if its adjusts to plays in that order, with a menu action required in between.
Thanks for trying Stan!