For a long time I was experiencing issues with the volume of instruments loaded within Kontakt. The volume slider liked to jump to a certain position, which many times was nowhere near the original preset volume. I generally dealt with the issue by setting the output slider within Kontakt to counteract the volume change, as I assumed it was based on a playback state or an event that I just couldn't seem to find.
I have since found out this is not the case. It appears that the volume slider on my MIDI keyboard has gone erratic. While I could replace the keyboard, it seems like it'd be a waste to buy a new keyboard just because one slider, which I actually never even use, has gone bad. I felt like there needed to be another way to work around this problem.
One solution I did find was disabling the volume slider through the advanced functions of the keyboard. This worked great, until I found out the setting was reset when the keyboard was powered down. This wouldn't be a huge issue if it weren't for the fact the advanced function settings are really difficult to work with. I really didn't want to have to go through the manual everytime I restarted my computer.
My current solution was utilizing a feature I didn't previously know existed in Cubase: MIDI filters. Within the "Preferences" window, there is a group of settings dedicated to filters for MIDI controls. By simply adding the volume slider into the filters, I no longer experience volume jumps.
Obviously this "fix" wouldn't be for everyone, as I'm sure many people utilize the volume slider. (I happen to have a second controller I use for volume, panning, etc.) But, it definitely is a nice feature to know about.