AECC Contours not showing up when referenced

[cadtag]

This is a new one for me... and is dwg file specific. Survey base file contains AECC Contour objects built from the existing surface. The Existing Condition sheet file references the survey base, but the AECC Contour objects do not show up, either in model space or through a viewport. Layers are on and thawed, not frozen in the viewport. Exploding the AECC Contour down to a LW Pline and it will appear in the sheet file.

Referencing the survey base into a different dwg, and the contour objects show up as expected. AUDIT shows no problems, and -purge R has no effect on the contour visibility. PROXYSHOW is 1

Same result in both Land enabled Map3d 2009, and Land Desktop companion 2009

[cadtag]

For what it's worth, Subscription support responded. they could replicate the problem, but not fix it. According to Jason it's a rare condition only known to occur in early versions of Land Desktop. supposedly due to unkown /unidentified corruption in the sheet file, audit and recover have no effect.

Of course I was running 2009 LDC, and started from scratch with my sheet file....

chaices are:
Either delete my sheet file and recreate it, or explode the contours to plines.