While working on no signal, I was looking into why the edges of a decal would sometimes disappear while viewing from certain angles in Godot 4.2.2. Looking into it, I found open issues godot/godotengine#81889 and godot/godotengine#73945 which look very similar to the problem I ran into.

For now, I’ve worked around the issue by simply adding additional padding to the decal texture.