I just bought the 'Synthogy American Grand' piano recently and did not experience any of the noise issues as described here.
Did Yamaha or Synthogy fix the issue?
Maybe it's just my earphones are weak on the 3K or other frequencies and it's masking the noise on me..!?

I have not tried playing it with the earphones cranked up past the point of the volume that an actual acoustic Grand would be, but I will try putting the volume up all the way when I get home from work today to see if there is any noise in elements 1 - 4. I will even increase 3 KHz on the EQ to see if I can hear it, and provide an update.

Looking at my previous post, I see that I misunderstood and thought that there was a separate element just for "key-off" release that may have been making the noise described above; however I now see that there is no key-off release elements/samples and that they are referring to the softest piano elements. I will also try different types of earphones & my computer speakers (I don't have speakers yet for my Montage, as I am saving up for the more expensive Adam A7x's).

What I can say at this point with what I've experienced so far, is that the 'Synthogy American Grand' Steinway piano is quite awesome and compliments the CFX really well! Love it so far...
If I do hear noise, I will fix it somehow rather than get a refund and not have it at all...

So here's my update:

After turning the volume up all the way, I could hear the 'noise' in the softer piano samples (ppp, mp), as described above. There is some noise in those samples that shouldn't be there and maybe it could be the FEG settings &/or EQ'ing that exaggerates it..!? Either way, Synthogy definitely captured some unwanted noise when they sampled the softer velocity layers of that piano that are found in the first 4 elements of both PARTs!

However, if I turn the volume up to where I can just barely start to hear the noise, especially playing softly on the highest notes, and then I start playing with some Forte and hit the higher sample velocity layers (elements 5-8) across the entire keyboard, the piano level is WAY TOO LOUD!!! In contrast, if I only set the volume of the pianos to the same as a real acoustic grand piano would be if you were to sit in front of & play one, then I can 'not' hear that noise at all (at least not through my earphones). Maybe it's just my hearing is starting to go bad in those frequencies, or maybe others have hearing closer to a dog's, but at the proper or at least a reasonable volume that is close to & not too much louder than an acoustic grand, I can't hear the noise at all..!!

While I had the volume turned up 'too loud', I did try lowering the 3K frequency (as suggested above) with a bit of a narrow Q on the EQ, and it seemed to get rid of the noise completely; however I didn't do an indepth check of other frequencies to find what the full range of frequencies that the noise resides in. Some quick adjustments to the FEG seemed to get rid of the noise as well, but doing so also got rid of some of the 'good' highs, making it sound too dull or dark.

Maybe this noise is much more pronounced through speakers like the HS8's that someone mentioned above, than it is through earphones!? If the noise is just in a narrow range around 3K, then that is curiously interesting to me, since it was around the 2.8K mark that I found the HS8's to be a bit harsh & honky sounding when playing pianos, thus I had that frequency notched down when trying to get my HS8's to sound closer to the Adam Audio A7x speakers that I had also tried and compared against. Without any EQ adjustment, the Adam's sounded sonically perfect to my ears and with my eyes closed gave me the experience that I was playing an actual CFX grand. I ended up taking back the HS8's because I couldn't get the frequencies EQ'd just right for pianos, so for now I am just using earphones until I have saved up enough to buy the Adam A7x's.

The Synthogy American Grand Steinway sounds way too awesome & realistic at the proper/reasonable volume level to even consider getting rid of & not using it. It is now one of my 'go to' pianos and I even like it better than the Bosendorfer.
My suggestion to those who like to play pianos mainly in the softer velocity ranges, is to turn the volume down to a level where an actual acoustic grand is at, to get a more authentic experience. If an acoustic Steinway is being played softly, then it's not just the tone that is softer, but also the volume that is naturally lower. Turning the volume up to hear the softer piano notes more loudly, to the point whereby you can hear this noise, is not a natural volume for getting the experience of an actual acoustic Steinway. If you sit at a Steinway and play softly, it will be at a volume much lower than the volume level at which that 'noise' can be heard on the Synthogy American Grand via a Montage/MODX synth...

I had more time to play around with the American Grand last night. Even with the volume up all the way on my earphones, whereby the piano is WAY TOO LOUD, and with all effects disabled, I could barely hear the noise on the 'AG Concert' performance. I had to bring the highs up on the piano to really hear the noise, or just bring up 3.75 K on the EQ. The previous day that I worked with that piano library and heard the noise, I was using the 'AG Rock' performance, which has the highs up on the EQ, as well as compression turned on.

I found (as another poster above did) that 3.75 K is where to notch down the EQ, with roughly a .9 Q to get rid of the noise. In most cases, for volumes at what an actual grand would be, the noise is not audible, but just to be sure/safe, I will likely have 3.75 K down a bit on both PARTs' EQs, so that when I have the 'AG Rock' or versions of that piano that have the highs more prevalent (& especially if compression is enabled), I won't be able to hear the noise at all through any speakers/earphones, even if the level is up a fair bit past what an actual acoustic grand's volume is.