Hello va3ets,
I have no previous experience with that sample set myself (although I imagine I might be able to get a copy from Gary Jordan if needed), but my initial questions would be:
- Are those pipes/notes borrowed from a different rank? You would be able to tell that by the sliders on the voicing screen showing as disabled (greyed out) for those particular notes when the rank for the (rest of the) keyboard's compass was selected.
- Does the problem occur with each of 'Original organ temperament' and 'Equal temperament' selected?
- Also, does the problem still occur if you temporarily disable the wind supply model on the 'Organ settings | Organ preferences | Wind supply model' screen tab?
- How about if on the 'Audio engine' tab of that screen you also set 'Random pipe detuning adjustment' to zero and 'Air flow randomization' to zero?
- If none of those things eliminate it, are you perhaps routing that portion of the rank to a separate audio output device (in case its sample rate is different from that of your main audio interface, for example)?