Hey man I also have the Rekordbox analyze issue.. mine sometimes shows 0 bpm and when I load it onto the nexus it says that I have to analyze it with rekordbox to be able to sync and see the waveform but rekordbox is stating i already analyzed it.
Rekordbox 1.5 will not work with the Nexus well because it misses the new analyze mode which is needed because the nexus uses extra data.