We use slabs for our ceilings, with cover fills for the ceiling tile patterns. Cover fills on or off depending on the view. In the past we used a separate fill on its own layer which was only on in RCPs. When we try to publish to AutoCAD to send RCPs to consultants, the fills do not show up. I tried creating new translators to give the cover fills their own AutoCAD layer, exporting them as all solid, exporting backgrounds as separate hatches, nothing seems to work. It seems like we will have to go back to using a separate fill to export the grids for our consultants, which of course creates potential problems with coordinating and updating.
It is all fills, not just our ceiling grid, we have other fills for gypsum ceilings and soffits, etc.
We do get a polyline in AutoCAD at the perimeter of the slab which should have the cover fill on it. The polyline is on the correct layer, etc. just no fill.
This is a bug. When saving DWG, the cover fill display is controlled by the cut fill display options. That is, if cut fills are off, cover fills will be off too. You probably have cut fills off in your view that you are exporting. If it's not a problem to turn cut fills on, then that's the workaround.