I have a Note 10+, barely 2 weeks old and the power buttons are stiff and won't rock. You have to press really hard with no tactile feeling of it working or not.
I saw an odd, temporary solution where you blow into where the power/Bixby button is and I did that and for a few uses, it does return the volume rocker back to normal but then it stiffens up again.
Any other suggestions?
I would recommend taking your device to your local Ubreakifix.
You can locate the nearest service center by visiting https://www.ubreakifix.com/locations
I actually got it working again. I noticed something sticky in the phone case in the area of the volume rocker. So I did the blow trick one more time and then with a damp cloth, I wiped the volume rocker area and it has been fine.