Exports some channels of a multi channel WAV as silence

Win 7 32 bit, Aud 2.03 previously 1.3
Hello I mention Aud 1.3 as I was having the same problem in 1.3 so it may be my finger and brain problem rather than Audacity.
I have created an 8 channel recording, and wish to render this to 6 channels for export as 5.LFE (not .1 as it will be 44.1 sample rate).
In Edit:Preferences Export/Import I have selected the multi-channel option and channel mapper (and metadata) I did this set up for both Audacity 1.3 and 2.03, and both give the same results. When exported the resulting file has 6 channels 4 of which are silence but channels 4 and 6 have the audio assigned from the channel mapper during export.
What am I doing wrong?

Hope you can help.

It works for me.

You have eight tracks but you only want six output channels.

Please state exactly which tracks you are going to mix into which channels to achieve that. The best way to do that is to set up the Advanced Mixing Options as you want it, then attach an image of that window. ALT + PrtScr to capture the window, paste into Paint, save as PNG and attach the image.

Please see here for how to attach files: https://forum.audacityteam.org/t/how-to-attach-files-to-forum-posts/24026/1 .