black stripes on texture when shadow enabled on mobile devices

Shadows not working as expected on andriod/ios browsers.
on Android there are black stripes when zoom in;
on ios the shadow is not displaying correctly.

Sandcastle example: 3D Tiles Photogrammetry.html

var viewer = new Cesium.Viewer('cesiumContainer', {
terrainProvider: Cesium.createWorldTerrain(),
shadows:true
});

var tileset = new Cesium.Cesium3DTileset({
url: Cesium.IonResource.fromAssetId(6074)
});

viewer.scene.primitives.add(tileset);
viewer.zoomTo(tileset);

Browser: safari ios

Operating System: ios

Start by running the “3D Tiles Photogrammetry.html” Sandcastle example with shadows enabled on the reported Android and iOS browsers, then zoom the tileset to reproduce the black stripes and incorrect shadow display. Trace the mobile rendering path for shadows and verify the result by confirming that the tileset renders without stripes and shadows display correctly on both platforms.

Written by the indexing model from the issue text.