It's there indeed.. I think many would agree..
I hear it as resonances (it's near the beginning of un-damped notes). The sympathetic resonances with those higher notes possibly accentuate that res (I hear it from c6 and a few more up).
To me, it's something a real piano does - the 'Model D' default preset is kind of closest (least especially treated) to the Steinway piano which was modelled. It's pretty certain, that an amount of that resonance was present. I don't hear it as bad, probably should add.
If it's definitely unwanted and you kind of can't un-hear it, click the "Equalizer" button, then go to the tabs.. /ResEQ" (and/or the ResDuration).. you can target the 'EQ ranges' of any resonant sounds you wish to attenuate or eliminate, pretty specifically with just that.
You can see the piano roll below, so it's easy as pie to see the range to 'cut'.. maybe just lowering the 'Res Duration' for a notch around those notes could be what you'd like.
Or try turning down the slider "Sympathetic resonance" a little (maybe try first if the above seems daunting).
Or if you're playing like you would a physical piano, perhaps try the 'Player' preset.. or if recording, use ones labelled with "Recording".. as those presets will have had focus on removing things like that... but for sure, each piano has a 'most like the original' preset.. and I definitely consider those like 'world library of piano' presets (snapshot of the thing without too much adjustment for particular use-cases).
Mostly I jump on default presets - and edit how I want - mostly for particular pieces/repertoires.
Hope that helps you get things more like the way you want to use Pianoteq
Pianoteq Studio Bundle (Pro plus all instruments) - Kawai MP11 digital piano - Yamaha HS8 monitors