According to an official at the HELP virey, and this is one of the few sources that believe can and should be😁, he says that VRayCarPaintMtl, can devour gigabytes of memory, under certain conditions.
In particular, it concerns the setting Flake map size bed .
Flake map size - parameter that determines the size of raster maps, which creates the material for storing the generated Flake (flake). The low value of the parameter, reduce the use of RAM , but it can create a tiling in Flake structure. Large same values require more memory, but due to this, tiling is removed. Be careful when using the Directional flake filtering method, as it can quickly take gigabytes of RAM for a larger map. See the examples that demonstrate the effect of this parameter.
Most likely, you have exactly this situation and you Flake generated map, simply do not have installed in your computer RAM.
You should either reduce the above-described setting, or do not use Flake filtering Directional, or install more RAM in your PC / laptop😁