I am getting an exception error whenever I attempt to place Raceway using the Variable Length option in my metric DGN file. I am using the GB dataset so my data files should be correct.
The error when placing Raceway is due to the resolution of the DGN file. Bentley's delivered metric files use a resolution of 1000/mm while the user file has a resolution of 10/mm, or a factor of 10x. Changing the resolution to the delivered 1000/mm will allow Raceway to be placed using the Variable Length option.
With the DGN file open, choose Settings > Design File > Working Units > Edit > OK.
Change the Resolution value from 10 to 1000 (per Millimeter).
This will likely result in the Solids Accuracy field (at the bottom) changing to 0.010000 Km; change this back to the delivered value of 1.0000 Km.
Note: The steps above will scale any existing elements, so it is recommended that you replace them with new versions at the modified resolution.