TextMeshPro Text (UI) becomes invisible if 3D Object intersects

So far, I have only used normal UI texts in my GUI. I now used TMP Text (UI) on an interface element and noticed a strange phenomenon: If I approach a sphere and walk through it, the TMP text disappears if the screen layer intersects with the sphere's hull, as if the mesh of the sphere overlays the text. It re-appears again once I am "inside" the sphere. What causes this behaviour? Other UI elements are not affected, only the text gets overlayed.