Now that you mention it, the drawings I am having the problems with, are drawings I imported a 2007 TIN from....
to be clear did you Import the surface from previous LDT project
OR
did you use the create surface from TIN operation?
either way the answer is MOOT, as....the parent object is a Surface, contained in that object are Contour Display Objects, which when extracted become the root object of a polyline...however the contour object itself does NOT honor or offer LTGENeration as a user controlled setting anywhere within the surface style parameters.
In short the LAST thing one may want to do...Extract the contours...wblock them out to their own file....set surface style to NOT show contours...XREF the extracted, and LTGENed polyline objects into the file....and Have a Nice Day!