Physical Materials Messing Up After Building Game

The game i am working on relies heavily on having the correct physical materials in certain surfaces for things like friction. To achieve this i have simply been adding different Physical materials onto the various materials through the details panel and then applying the materials to my various meshes. This works perfectly well when i play the game within the editor, but once i build the game, its hit or miss. Some surfaces retain their physical properties whilst others completely lose them.

In the past, to prevent this from happening i have simply been checking the “recompute normals” option in the details panel of the mesh, which worked fine despite not really understanding what was actually going on. Now i’m starting to use more complex meshes for my levels and they have smoothing on them from Blender (which i’m using to create my levels) which creates a new issue for me. When i import the mesh, everything is fine but once i apply the “recompute normals” to fix my physical material issue, it remove all of the smoothing form my mesh.

So now i’m stuck in a situation where fixing one issue breaks the other, and neither of the issues i properly understand. In an ideal world, id like it if someone would be able to help me fix (and more importantly, understand) the initial issue of physical materials not working in the built version of the game. If not that, they id like to know if its possible to use the “recompute normals” options whilst retaining the smoothing on my mesh.

If any more info is needed please ask and il reply asap.

edit: running on 4.19

Thanks in advance for any help!