The MusicType "DLC03MUSFactionChildrenOfAtom" does not have a "WNAM - Fade Duration" value associated with it. This means, when crossing the threshold between Worldspace Cells with DLC03ExtFarHarborGlowingSeaAUDIO01 defined as the Region (i.e NucleusExt01 and generic Wilderness), the music will abruptly stop before playing the next track.
A FadeDuration value of 12 (seconds) would keep this in line with other exploration tracks and leads to a proper feeling of transition.