PhotonView Unreliable On Change Constantly Updating Despite No Changes

Crukiln

My game is a card game and has no moving parts at the moment. I instantiate about 40 scene-owned cards at the start of the game using:

GameObject cardInstance = PhotonNetwork.InstantiateSceneObject(card.name, new Vector3(0f, 20f, 0f), Quaternion.identity);

I've incrementally reduced my Card GameObject until it literally contains nothing:

public class Card : MonoBehaviour, IPunObservable {
    public void OnPhotonSerializeView(PhotonStream stream, PhotonMessageInfo info) {
            if (stream.IsWriting) {
                print("Card stream size: " + stream.Count);
                // We own this object: send the others our data
            } else {
                // We don't own this object: receive data
            }
    }
}

In the console, it still continuously streams the printed message hundreds of times a second:
"Card stream size: 3"

Reiterating, my game has no moving parts at the moment. The card object gets instantiated and then just sits there doing nothing. No values are being updated at all. The PhotonView attached to my Card Prefab is set with the Observe option "Unreliable On Change" with one Observed Component (the attached Card script).

Really stumped by this. This applies to other (simpler) networked GameObjects as well. I've tried removing Box Colliders, Sprite Renderers, Text, Raycasters, Canvases but nothing seems to work.

Any pointers would be appreciated.