Thought i'd share this experience:
One of our engineers uses a 10 year old engineering package which obviously cannot read any of the recent cad formats. We set our export translators to translate to model space and acad2000 dxf format.
The engineers could open it but had problems with wall and column lines missing (very serious indeed).
We tried a whole lot of different options with the translators, without any luck.
What worked was when we copied and pasted the plans into a worksheet and then exported to dxf. By doing this, everything gets converted to 2d elements, including walls and columns. I also do a search and delete of all unnecessary fills.
Aziz Tayob Architects
AC23 INT rel 3003, OS X 10.14.6 iMac 3.3ghz i5 dual monitor, 24GB RAM