Greetings!
You made an excellent tool and great progress in Gran Turismo series reverse engineering, congratulations!
I got some bugs with exporting to OBJ:
Car a2azn.cdo looks good in viewer:
but loses tail lights in OBJ form (in fact, they hidden behind a trunk polygons, i delete one for screenshot):
and some details is missing (same way) for a222n.cdo, but there's another problem with car name on the trunk, it's intersected in viewer too:
Most of night versions of cars also have problems with lights glow.
For OBJ i think it's caused by low precision - 3 symbols after dot it's really low, it's better to use 5-6 symbols.
But for viewer IDK, maybe PS models have low precision in overall?..