I assume this is a bug. Everything looks correct in the editor or photo mode but not during gameplay.
This happens on the 14 volkswagen golf also, i have a police paint i made for it and it looks fine in editor and photo mode but live the rear quarter panel distorts the vinyls and its really irritating .
at 0:44 in your YouTube video; I’ve also experienced this with my RX-7 ‘Black-ice’ design. The racing Stripe on the hood doesn’t align all the way with the bumper in cut scenes.
Here’s another… McLaren P1. In-game on the left, photo mode on the right. (The blue doesn’t reach down to the bumper on the right either but that’s because of how the model is. But on the left it’s clearly all messed up.)
Also see the wing:
Try restarting the game in quality video mode (30fps). I think Forza 4 uses a more complex model for quality mode and a simple model for performance mode. I spent all day trying to figure out why my paintjob didnt look the same in photomode vs driving it. The paintshop & photomode use the complex 3D model always. Thats my theory anyways.
I’m playing on PC.
This issue has been a thing on multiple cars in multiple Forza games over the years. And has never been completely fixed for all cars. All we can do is deal with it.
This happens because - unless you are playing on the One X or a high-end PC with the ability to run the game on rather high settings -Horizon loads a model with a lower level of detail (LOD) for the player car during gameplay. Usually this doesn’t create any issue with player-created liveries, because the LOD1 gameplay and LOD0 photomode / LOD-1 Forzavista models use what appears to be the same “outer” shell for the car, but in some instances they seem to rather aggressively have reduced the poly count around certain areas, or more likely stacked it with the texture mapping and the polygon welding (as seems to be the case with the P1’s nose).
I doubt this issue with the LOD1 models will ever get sorted - I suppose it’d be an outrageously expensive and time-consuming task to review all the models presenting those flaws, and after all, few people even seem to notice.