OMG Thank goodness someone else noticed this.
It's very annoying and it produces an almost "organ pad" type of effect. It only happens when using the pedal though. If you use no pedal and just hold the keys down it sustains normally.
I wrote Yamaha over a week ago and this is what they came back with.

Hello Darrin,

Thank you for your Yamaha inquiry.

Please see my answers below to your questions.

__

I have a CP88 as a loaner right now until my brand new one arrives at my local music store.
I have two concerns that I am hoping someone there can assist me with.

1) the first CP80 sample or Comp CP80 is an amazing replica of the original CP-80. However, I have noticed that when you use the hold (damper) pedal it sustains much much longer than normal and produces and an almost "organ" type effect.
As opposed to actually holding down the keys it sustains on a more realistic level.
Your other piano samples do not do this when using the hold pedal so I am wondering if it's just a "bug" that needs fixing??
>>>I am not aware of a problem with CP80 sample. Did you update the CP88 loaner by any chance? There is a new firmware that fixes some bugs and adds a Yamaha C7 piano sample and some more EP's
https://ca.yamaha.com/en/products/music_production/stagekeyboards/cp88_73/update.html#product-tabs

I checked this with your second CP sample and it doesn't do it when using the hold/damper pedal and it sustains normally.

2) The action on this CP88 is incredible the only thing I am concerned about is about two things....one, 3 of the keys are "clicking" meaning there is a definite defect in them.
Since this is a loaner I will live with it but my concern is that I have only had this is happening already so wen my new one comes in am I to expect faulty keys down the road???....two, the keybed is very loud...to the point that when I play hard and also release the keys the noise is resonating through my microphone. Again, is this normal or a defect and if so will I expect it with my new CP88 when it arrives?
>>>First and foremost if you have a problem with your keyboard we are here to take care of them. I do not suspect that you would have a problem but clearly, there is something wrong with the CP88 that you have. Our keyboards are not quite and the more expensive that it gets it really does emulate an acoustic piano action - which by the way is not quiet by any means. What I would suggest is that you wait until your new CP88 arrives and please mention to the store of which you purchase that you have spoken to Yamaha and it looks like it would need warranty work.

I am hoping someone out there can help/assist me with my concerns. $3400 is an awful lot of money when issues are creeping up already in the almost month's time that I have had it (loaner).

Thank you and kind regards,
Darrin

I haven't written them back but I did check out a CP4 and it's CP80 samples sustain normally.
It's GOT to be a bug.

Hi Darrin,

it seems that not too many users play the CP80 sound!
😉

The sound itself is pretty nice but this
BUG is annoying.
Hopefully Yamaha will correct it with the next update!

Markus

p.s. I have the latest OS installed.

Hi Markus, Sorry for the delay.
Yes I guess not many folks rely on that sound besides you and I.
So it seems that CP80 1 is the bad one and CP80 2 is fine.
I am gonna start a petition to get that bug fixed. I hope you'll join me to have Yamaha do an emergency firmware upgrade because that bug is unacceptable. I didn't pay over $3000 for such a flaw.
Talk soon
Darrin
Give me a shout sometime and we can swap piano recipes...LOL
88fingersd@gmail.com