Why do any number of Studio One v4 instruments have a perceptible and very annoying background noise floor in them?

There is an annoying "background" noise in several of the Studio One v4 instruments -- e.g., several pianos that cannot be eliminated or masked.  It renders the instrument useless and forces me to look for alteatives.  I like the basic sound, but the quality is below par.  Is this a known problem, or am I possibly doing something to cause this?  I've checked the issue on multiple computers I own since I have several locations in multiple states where I do work in the studio. Recent Questions...