Did you check on bars 5, 13 and 14 about what I wrote?
Yes, I think it's related to how this particular RealTrack was recorded. The notes are quite sparse.
I listened to the soloed vibes demo in the RealTracks picker. The performer doesn't start every note on the first beat, sometimes he plays as a pickup note (like a push). This may affect the result you are hearing when you have a chord on the first beat of the bar. I also tried adding a chord on the 4th beat of the preceding bar and this improved the result somewhat. Not perfect, but perhaps an improvement.
Maybe someone from PG Music can jump in and clarify why you are having so many issues with this style? They will know exactly how the track was recorded.