Terrian blocks dissappearing after baking Navmesh

Hello, I baked a navmesh for units in my RTS project and after starting the game, random ground layer objects started dissappearing, even after clearing the navmesh. Its strictly a visual thing, the objects are still there, the unit can run over them, even though they are invisible and after I move the camera, they start popping back in and different ones dissappear. Not entirely sure if thats because of the navmesh but since it happened after I baked it, I suppose it is.

Any idea what is causing this and how to avoid it/fix it? Thank you very much