Thanks for your answer. Much appreciated!

1 and 2 are not the problem, there's an audio track with just vocals, and the tracks are not frozen.
3 How does this remapping work?
4 It's only one particular track (acousic guitar). I tried the "simple" option but is keeps playing the 7th (G) sometimes.

In the realtracks prefs the box for "jazz up" is unchecked. It's not a jazz realtrack anyway but a country track, so I guess it shouldn't matter.

Best regards,
Jos