So I have an early press copy of Forza Horizon 4 and I've been running a few tests. There is a car in the game that glitches out on Forza Horizon 4 with AMD cards but not with Nvidia cards. I have not had a chance to test all of the cars in the game (there are a ton lol)
PC setup
2700x
Asus ROG Crosshair VII
32 GB Ram of G.Skill's Hyper X 3200Mhz (Running at 3200mhz)
GPU's tested
AMD R9 Fury X
AMD RX Vega 64
Nvidia GTX 1070
All settings are stock on the GPUs
Graphical settings are the following
Forza Horizon 4 9_27_2018 7_40_02 AM - Streamable
Here is the issue in 18.9.2 and the RX Vega 64
Forza Horizon 4 9_24_2018 5_16_43 PM - Streamable
Here is the issue in 18.9.3 and the RX Vega 64
Forza Horizon 4 9_27_2018 7_32_55 AM - Streamable