Hi,
To me it sound like you have set the Tuning parameter at the top of the application to max. Then the overall tuning is being raised a quarter note. This tuning will also show in the Tuner, if it's set to 440 Hz tuning.
If you then apply modultion to the same parameter, then you will not get any further modulation result, as that's how far the overall Tuning parameter go.
Modulating the seperate Operator Pitches with aftertouch will/ should give a different result. But keep in mind that the result also depend on the choosen algorithm - (how the operator is being used, and if it's used at all).
The 440 Hz overall tuning is when the Tuning parameter is set to the Center position.
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In case it's not about the above, then which Pitch are you talking about? Tuning or Operator Pitch?
Which plugin do you use? VST2, VST3 or...? Do you have the issue in standalone mode?
Which OS do you use?
No matter what, then you should not have a pitch change before you add modulation.
Can you hear the pitch change when you raise the modulation amount, while you hold the note? If not, then it look like, it's about the above mentioned Tuning.