Our pup is now 7 months and still pees and sometimes poos inside. (And then often eats it which is a whole other thread!) Luckily we have hard floors but oh my god it's really doing my head in now. He just doesn't seem to learn! I use simple solution to clean it up but it makes no difference. It's less than it was and he sometimes has days when he doesn't do it at all and I think we've cracked it then he will just pee everywhere and I feel hopeless again. I know they are notorious for it but was hoping to have got it by now.
If you have a shih tzu, how old were they when they were reliably trained?