Im not entirely sure what the issue is with the default Quixel Shader but for us it has a history of breaking so we started building our own. This is fairly simple to do unless you desire to use a form of displacement/POM in which case I would look for such a shader on the marketplace and use it with Quixels Decals.
There are allot of tutorials on youtube which I would recommend. Just search for: Spline Roads, Quixel Decals UE5, Fasttracktutorials decals. If there is a specific problem just drop a comment with actual screenshots and a clear description of what is going wrong. Cheers and have fun.