I consider it a bug, and an old one at that, but if you delete the _lenx_nominal attribute from the Definition, the value should be right after a redraw.
@pcmoor is correct that it’s best not to scale a DC from within.
Save a copy of your model if you try this - no one can be certain what the results will be. That said, I’ve not had any troubles deleting any of the *_nominal attributes.
Sketchup.active_model.selection[0].definition.delete_attribute("dynamic_attributes", "_lenx_nominal")