Why is my mesh acting like it has a bumpy surface?

I’m working on a golf prototype game in which the ball is pushed in the x,z axis (via AddForce, force mode is impulse). The only force acting in the y direction is gravity (set at 98.1 to make the ball fall realistically as upping the mass does nothing).
I’ve imported a large single mesh from Blender into Unity and on the flat areas the ball is hitting non-existent bumps everywhere! The ball has 0.6 bounciness and maximum bounce combine (which is the 0.6 bounciness) on its physics material and is pushed ONLY in the x,z direction. Why is it hitting bumps along a flat mesh that has no edges/vertexes on it (it’s just one large face). I would understand if the mesh had multiple vertexes/edges, made up of many faces, but it’s just one large face inside 4 edges/vertexes.

There’s no such thing as a quad or n-gon in Unity. Unity triangulates all meshes. It is possible the issue you are observing is related to Unity’s automatic triangulation.

It’s best to build your mesh topology in Blender as you wish, then convert all faces to triangles - in the most desirable configurations - by hand and/or with the “triangulate faces” option (and its sibling commands) in Blender’s “faces” command menu. That way you control how the quad or n-gon is triangulated.

It’s entirely possible that there are other issues going on for you, though. “Bumpy” isn’t descriptive enough to communicate anything meaningful. If this suggestion does not resolve the issue, consider adding a video of the issue occurring, screenshots of your mesh wireframe, and a more carefully-worded description of your scenario and issue.