TrueHD Atmos tracks multiplex to mkv instead of mka

First time i've come across this. When converting the demuxed .thd atmos tracks from a blu-ray music album, two of the tracks are identified as video so won't convert to mka:

Container - AVC/H.264

Video codec - AVC/H.264/MPEG-4p10

Properties - 12006x32 pixels (other track says 32x28 pixels)

If I play the .thd files in Foobar2000 they play the audio normally. If I convert them to FLAC, they also play normally. Can you help me find out why just these two tracks have this problem and if possible find a way to output as mka?