2006 Model Space Regen Zoom Extents

I have a drawing of a stretch of highway in Model Space. I examine small portions of the drawing in various Paper Space viewports, scale is 1:100 and the viewports are locked. When I go back to Model Space, the drawing Regens and Zooms Extents. This is very aggravating. This does not happen to any of my other drawings or a new drawing. I know there is a switch somewhere, I just don't know how I turned it on. I thought it was Regenauto, but no luck.