Volume problems on Yamaha YC 61 with vst apps

Why do some notes change volume on my vsts after shutting down and restart of my computer?
I use Steinberg 2.1.4 usb midi driver, Yamaha YC 61 keyboard, Dell Windows 10 pc with Realtek audio sound, and acousticsamples VTines Mk1 vst, also Pianoteq7 pro piano vsts. VTines and Pianoteq allow adjusting volume of individual notes. After I adjust all notes for same volume, using fixed velocity on the YC61, after I shut off the computer and restart, a couple of notes on these vsts have become louder, and I have to adjust/edit the volume lower for those notes. I don’t know if this
changing volumes after restart is caused by the vst apps, or the Steinberg driver, or the Windows 10
operating system (Realtek sound driver, etc). It is an annoying problem, having to readjust some note volumes every time I restart the pc, keyboard, and vst apps. Anyone know how to fix that?