Awwww that sucks so bad that your dog's excellent behaviour is ruined >_<.
                           
It's funny but I only realise it after I have my own dogs, they have their own temperament and no matter how often I bring them around to walk outside, it doesn't feel like their behaviour can improve significantly. Though I do notice that they become less secure when I haven't walked them in a few days because I'm lazy the weather is too cold so it's always good to walk often with them.    
                           
Thanks for letting me know more about your dogs, fyn :).