Need help with good hears please

If it was not enough for deciding, I'm adding 2 files with a performance for comparison.
- One with the guilty C5.
- Another one with normal D5.

Wouldn't call the C5 unusable, but there's definitely something wrong with it, I agree.
Here's another illustration.

There's lots to be said for propriety sample playback software I suppose (although I can't think of much), but if you run into something like this and the developer can't or won't acknowledge the problem, it can get frustrating. In the old days, when most libraries came as fully editable patches, you wouldn't have to bother anyone with an issue like this and you simply replaced the offending sample by remapping one of its neighbours.

What I usually do with little annoyances like these, is to load up a second instance of the software — in this case Pianoverse —, assign all the C5's to that second instance, transpose them one step up or down and then retune Pianoverse one step up or down in the other direction. (Transposing Pianoverse doesn't work as you end up triggering the same (offending) sample as before. You have to use the Tune parameter and slide it all the way to the left or the right to retune it by a semitone.)

But again, unless you have a piano part where the C5 is very present in the dynamic range where the note sounds at its worst, I wouldn't call this a major problem. But certainly a problem.

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Thank you so much for your feedback, and thanks a lot for providing another illustration. I will definitely forward it to the support in my next email.
I think I call it major because every time my finger hits the key my brain focuses on this transient now and I'm just hearing that, so I could be a bit biased. I'm definitely going to try your trick, that's a super cool idea. Thanks again!
Btw, I found other issues I didn't mention in this thread, which I would call minor this time:
- D3 sounds slapped at any velocity, it sounds weird if you play delicately with some notes around in the same octave.
- F#1 release sample got a nasty high harmonic.
Tried the whole library with a subscription and loved the NY Steinway closed mics. Perfect match for my taste. But the C5 was preventing me to buy it. Now, with the trick, I will go for it.
Hopes the upcoming Hamburg one will come without any big defects. Hopefully, I could subscribe again to test it before buying it.