They mentioned earlier that the reason they couldn't just transfer Valkyrie's memories into another body to bring her back was because there was no way to transfer the emotions attached to those memories, essentially meaning that the new body would be a brand new person with someone else's memories inside it. My theory is that this is what happened to Ziggy. Someone repaired his body and essentially made a new robot that had all the memories of the original, but with none of the emotions attached to it.