### Godot version

4.1.1

### System information

Meta Quest 2 - GLES3

### Issue description

When writing VR applications on Godot 4 using gl_compatibility, skeleton-driven meshes like hands are often rendered corrupted, or sometimes update slowly.

### Steps to reproduce

The godot-xr-tools demo projects have these issues in the climbing/gliding and pointer-demo scenes if the project is switched to gl_compatibility mode and run on a mobile VR headset.

### Minimal reproduction project

The godot-xr-tools demo project has been the testing project for this issue.
MultiMesh *multimesh = multimesh_owner.get_or_null(p_multimesh);
	ERR_FAIL_COND_V(!multimesh, Color());
	ERR_FAIL_INDEX_V(p_index, multimesh->instances, Color());
	ERR_FAIL_COND_V(!multimesh->uses_colors, Color());
	_multimesh_make_local(multimesh);
	Color c;
	{
		const float *r = multimesh->data_cache.ptr();
		const float *dataptr = r + p_index * multimesh->stride_cache + multimesh->color_offset_cache;
		uint16_t raw_data[4];
		memcpy(raw_data, dataptr, 2 * 4);
		c.r = Math::half_to_float(raw_data[0]);
		c.g = Math::half_to_float(raw_data[1]);
		c.b = Math::half_to_float(raw_data[2]);
		c.a = Math::half_to_float(raw_data[3]);
	}
	return c;
}
Color MeshStorage::multimesh_instance_get_custom_data(RID p_multimesh, int p_index) const {