Hi,
It looks like somewhere in your logic you are instantiating this clones. if x and z works, and y doesn't, then typically, isolate y and make a special scene to see if the bad behavior persists and then you can track it down, don't try to debug in your full game, this will be too much.
IF y works on its own in a scene, then it's definitly a problem of logic in your game, and you'll need to patiently analyze and put debug log in the actions you use to instantiate everything, this would be how I would start, edit the action to log everytime you instantiate something, and then compare with what's in the world.
Bye,
Jean