Hi jaakjensen,
This is due to playing non-scale tones, which Quadravox does not support. There is not any expected behavior we can point to for this reason. When you set Quadravox to a pentatonic scale with Pitch Tracking enabled and then play notes outside of that scale the algorithm makes a decision regarding what to play based on the chosen scale rather than maintaining the direct interval relationship as it does when you play a note within the scale.
We do hope to add support for this in a future software product, and we currently offer key quantization in a number of hardware algorithms, specifically Diatonic, Quadravox, Quadravox+, VocalShift and VocalTune.
