Why don’t you have a dedicated bugs forum section?
macOS 10.14.6 (18G6042)
When importing a 5.1 DTS file into Audacity and exporting the 6 tracks as WAV or AIFF, Audacity adds an obsolete channel to the L, R, Ls and Rs channels. Those obsolete channels are then called L.L, R.R and so on, the obsolete channels are filled with silence only.
Because 99% of “bugs” that are reported turn out to be something else (faulty equipment / user error / incorrect settings / misunderstanding / other software problems / bad drivers / … the list goes on). It’s more informative if we at least know whether the problem is on Windows, Mac or Linux.
So you import 6 channels and on export you get 7 channels?
I tried importing a sample 5.1 DTS audio (from an .mkv file) from the internet (the digital theatre). It imported as six tracks named, xxx 1, xxx 2, etc. (Which played in mono very nicely, by the way).
After changing my Preferences > Import/Export options to “Use Advanced Mixing Options”, I exported the tracks as .WAV. When I re-imported the new .WAV file, I got my six tracks back just fine.
However, if, in the export diagram showing the various channels, I adjust the number of exported down to 5, then back up to 7; the resultant file has 7 tracks with the last two zeroed out. Do you suppose this is a bug or the way it was designed to work?