Alignling two models exactly

I’m trying to position a model on top of a photogrammetry asset, both are from ION…
How can I do this? I have both in Blender positioned, but when I upload the tileset to ION the Cartesian3 changes…
eytanmann.xyz/herodion/

(async () => {
    try {
        // ...

        let tileset = await Cesium.Cesium3DTileset.fromIonAssetId(1750337);
        tileset.maximumScreenSpaceError = 1;
        viewer.scene.primitives.add(tileset);
        
        const assetId = 1954186; // Replace with your asset ID
        const resource = await Cesium.IonResource.fromAssetId(assetId);
        const entity = viewer.entities.add({
            position: Cesium.Cartesian3.fromElements(4438223.600063435, 3135682.555670942, 3329316.5869328612),
            model: {
                uri: resource
            }
        });

    } catch (error) {
        console.log(error);
    }
    
})();

the Cartesian3 changes…

Which Cartesian3? Are you sure you’re using the same reference system?