The gpu-instantiated artifacts will disappear when I rotate the model in cesium

gltfpack is very strong, so I want to use it to support meshopt, meshquan, etc.
But the gpu-instantiated components will disappear when I rotate the model in cesium.
Why?

PS:3dtiles(1.1), cesium(1.99), the gltf support the following extensions:
EXT_structural_metadata,
EXT_mesh_features,
EXT_instance_features,
EXT_mesh_gpu_instancing,
EXT_meshopt_compression(gltfpack),
KHR_mesh_quantization(gltfpack),
KHR_texture_basisu(gltfpack),
KHR_texture_transform(gltfpack)

1.It has not been processed by gltfpack.
model_no_gltfpack
model_no_gltfpack.zip (29.8 MB)

2.It has been processed by gltfpack.
model_gltfpack
model_gltfpack.zip (5.3 MB)