pottie training

Question
About a year ago I found a german sheperd while at work. After days of asking around no one laid claim so I took her in.  I have had german sheperds in the past so this was not anything new for me.  After a extensive vet check up and a good cleaning at the groomer I brought her home. It is believed that she is 100% sheperd (determined by marking and whatnot). Her is the problem while at my home she is very obiedent and calm doing all the right things, however, while at the dog sitters (my parents) she becomes somthing different and constantly will use certain areas of the house as her private restroom even after coming in from outside.  We have tried many ways to break this but have not been able to do so.  We have tried cage training where if she doesnt do her buissness outside she goes in the cage but she tends to go enough outside to make use happy then comes inside to finish up.  Someone please help, is it possible this will stop (along with other less aggrivating behaviors) once shes fixed?

Answer
I am sure part of this relates to her past, along with being bonded to you, and perhaps not being comfortable away from you and with your parents.  Shepherds just do not accept other people like say, a Lab would.  How much time does she stay with your parents?  Maybe give up and pretend you have to leave her by herself in her crate.  She may be happier safe in it than with people she doesn't trust.  They can still give her plenty of breaks.  In time, she may come to accept them and be more comfortable with them.  Have they been leaving the crate available so she could retreat to it?  If not, that could help.  

Another approach would be for your parents to drill her in obedience.  If she has not been trained, it might be a good idea for your parents to do it.  The dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/