Null Values from "Unknown" Quality Overlay

I am having a problem with null values being reported when my quality overlay goes to “Unknown”. It forces “null” into the value and updates the SQL database with “null” which causes problems throughout my project.

When the quality overlay is any of the red overlays the values don’t go to null, only during the green “Unknown” overlay.

Can you elaborate on both:

  1. what system specifically do you mean when you say it forces null into the db
  2. what problems are the nulls causing?