I am currently simulating the aerodynamics of a vehicle for a project. The setup is almost complete, but I am having difficulty generating a high-quality mesh. I can mesh the entire geometry without enabling the boundary layer option, and the elements are about 99% perfect. However, when I turn on the option "Add boundary layers", the mesh quality drastically decreases, with about 55% of the elements being faulty.

For reference, I am using the following settings and I am using a Hex-Dominant mesh: maximum mesh size of 500 mm, minimum mesh size of 4 mm, a first layer thickness of 0.04 mm, and 20 boundary layers.

I am very much looking forward to your responses.