Glad you got your problem sorted out and fixed. And, thanks for posting your resolution.
As I said before, the Source Number of Channels setting has also been troublesome for me, as I am sure it has been for others. So, I do not use it. I use Zoneswitch instead between 5.1 and 7.1 fixed output zones in DSP Studio, and that works perfectly for me.
But, I saw the JR channel mapping issues discussed in a thread here back in 2011. A decision was made then after discussion and user input for how to implement it. It may not have been the optimum decision based on accurate knowledge of how recording producers were using the Channels metadata on the disc itself. They seem to use Channels = 5 for 5.0, 6 for 5.1 and 8 for 7.1, based on a quick view of my library. (I have never seen a 7.0 disc.) They also seem to add null surround or center channels on the disc for 3.0 and 4.0 playback, using Channels = 5. Stereo, of course, has Channels = 2. So, there is an industry-wide difference between the integer specification (2,5,6 and 8 is all I have seen) used in Channels in recorded metadata and the way that we commonly refer to the output system layout (2.0, 2.1, 3.0, 4.0, 4.1, 5.0, 5.1, 7.1, plus maybe a few other possibilities). The two schemes do not quite mesh, and the only way for JR to know what output channel alignment to use is in the output spec you apply in DSP Studio. Incidentally, there may possibly also be some oddball discs out there that use the channel alignment and Channels metadata differently. I hope I never encounter any.
Bottom line, though, the current functioning may not be to your liking, but I think changing it at this point might cause a world of problems for existing JR users, since it has been the way it is for over 5 years. And, there is an available solution that makes sense if you understand the issue. However, Source Number of Channels as the DSP Studio output spec, easy to use as it is, may lure people into making the wrong choice for Mch unknowingly.