About sprite3d show on ui

I want to show some sprite3d on ui and i make it works(modify the meshcommand’ is3D), but when i make it with normal sprite3d, the ui sprite3d will have a transparent make of the back sprite3d,

see this https://github.com/cocos2d/cocos2d-x/issues/12331

who can tell me why, or how to make it work?