Imported Collision Not Working

I’ve imported my own custom collision for a road I have made as the Unreal automatic collision generation was not great.
This is the first time I’ve been doing custom collision and I think I understand the process but some things just don’t make sense to me.

I understand that the naming conventions need to be good and that the shapes need to be convex. My understand of convex is that if you were to draw a line from one vertex to any other then the line will not leave the shape.

This is one part of the road that I have uploaded the screenshot of. The rest of the object works fine with collision, but this area is not working and I have no idea why.
As you can see from the pavement that has a similar curved shape works fine and has a very similar mesh, which makes why this shape isn’t working a bit of a mystery to me.

As a side question, is there any easier way to create custom collision. Because a lot of this process seems needlessly finicky, and in this case, a lot of crossing fingers hoping the engine doesn’t just not accept the mesh and decides to automatically slice up your collision randomly.

Just answering my own question here.
Turns out my mesh was too thin. The mesh was only a centimetre or so thick so clearly upon import when the engine figures out if it needs to fill any holes to make the object convex it was having trouble with such a thin object.
I expanding it to be about half and inch thick and it works fine now.