This will probably be a no answer, but can ghost pets breed with each other or with live pets? Would be fun if they could, but i'm really not expecting it and since i haven't been able to play the Sims 4 for the past few days due to work i can't test it.
As for the expansion, no major problems or bugs that i've seen so far. Made a cat that i had a few years ago and trying to teach her not to jump up on things. (Just like my real one did lol) Haven't been able to get into the Vet career yet though but may try it with my Sim's daughters.