So I've been using AI since CS3, and I'm very proficient.  Even as a skilled user, sometimes my objects somehow get marked for overprint fill.  Seemingly randomly. 

Here's an example.  I have an art file for packaging that is 4 layers, each for their own flavor.  I copy/paste in front information that is common to all layers, and on one of the layers, the copy/paste in front got marked for overprint, while in the other layers it did not.  It was the same copy/paste across all 4 layers.  This is downright dangerous because if an allergen warning gets marked for overprint randomly and does not appear on the final print, it would cause our packaging legal problems if it's not noticed.

Additionally, one might think prior to exporting as a print file, that you select all and uncheck the overprint box, however it has three settings: check (overprint), unchecked (not overprint) and a dash mark which I have no idea what that means.  I assume it means something selected is marked for overprint, while other things are not.  So I select all and uncheck that box to mark everything as NOT overprint, but it just leaves the dash there regardless.  So I have to widdle through the file selecting objects to find the one that is overprinted.  This is ridiculous.  Mind you, I built these files from scratch, and I NEVER use overprint.

In fact, I never use the attributes panel for anything, and I have no idea how this is happening.  Overprint is extremely dangerous in my line of work as objects that appear on screen may not really print due to having been marked for overprint.  Is there a way to completely disable this dangerous feature?