Syncing nuo-stems into traktor not working

I’ve uploaded a working nml after importing into tractor. However, what Im now seeing is that lexicon is not importing the stem files at all.
I have created a ‘Lexicon test’ playlist with 3 tracks in it, the original file I sent, another stem track and finally a standard aiff file that Traktor has generated its own stems on. The only file that shows in Lexicon after doing an import and selecting just this playlist is the aiff file. Both m4a stem files are not added to the Lexicon playlist or the collection at all.
This is different behaviour than before.