"fatal error: unable to get original node positions"

I've been working on the Roamer Sport and getting it updated (again...), although there seems to be an issue somewhere. The vehicle does not appear when I try spawning it. There aren't any reported code errors, although I do get "BeamNGVehicle::spawnObject|fatal error: unable to get original node positions" and a bunch of duplicate part errors (although that's beside the point).

• I'm using copies of the 0.5.6.1 Roamer files.
• The mod files are in a "roamer" folder, just as they always have been since the second iteration, so that one can switch between the long and short frame in the parts selector.
• All of the old 0.5.3.x (?) files are in a subfolder labelled "archive" so they should be ignored.
• I did make node position adjustments, although that's basically it. Several recent tests with node/beam changes to fit the Sport frame worked perfectly.

I'll try using clean copies again tomorrow and see where I went wrong.

(Also, I changed the resolution of the game window spontaneously while writing this, and now the game UI doesn't work either. )