Found the problem! Inside your lane markings group, after you’ve joined the cyclical and straight lanes together and convert them to a mesh, you’ve got the Curve Line node that’s providing a “Profile” to skin the curves. You have a value of 1 in the Z axis at the end. This is skewing your profile and making it a bit funky, causing the issue. Get rid of that 1, set it to 0 and it works fine.
