DGNExporter: Split DGN libraries
As I said, you would need to create a 'Top Mesh' feature definition for the corridor. Easiest way is to amend the setting of a feature definition that you already have e.g. Design.
OK, for anyone else having similar problems (or maybe I'm the only one to ever have problems!)
I removed the offending windows printers from the machine and reinstalled them using the Update Driver option. I also deleted their user preference files…