A short while ago I updated to the latest release of SO2.
Since then, on MIDI tracks triggering VSTs totally at random a crackling noise can be heard. This did not happen in the previous release I used. I checked with old songs that never gave problems even in SO3.
In the forums this is reported as a problem for Audio - but in the test songs there is no audio. So increasing buffer size won't be a solution -- I nevertheless increased it, but still crackling.