My German Shepherd acts differently with my partner

Hi Tom and welcome to the forum.

I had similar issues with my first dog at around that age, possibly a little younger. I had my dog 6 - 8 months before my girlfriend moved in (she is still my girlfriend after 40 years, they never leave ha!). The dog would stop her from going out of the room and generally moving around the house. It was when I wasn't around and the dog thought 'dads out so I must therefore be in charge as after all I was here before she was'. (dog logic). I told the girlfriend to take charge and she fed him, gave him treats and walked him so his welfare was in her hands so he towed the line from there on in. Also back to basic training. Go right back to the beginning whether your dog knows stuff or not. This is good practice every time your dog has a spell of misbehaviour, or thinks he knows better than you. This will be throughout his life may I add. At this age in particular your dog is becoming an adolescent, (and we all know what that's like), and on top of that he is going through one of the many fear stages that they get in their younger life. On a lighter note your dog will mellow and enjoy life by the time he/she is 3 years old. That was the case with mine it was like flipping a switch to normality.

Tell us more about your dog, his name, colour, pedigree name (if you want to) and post some pictures...we love those. Also tell us more about yourself, what you do, a rough area where you live just in case there are some group walks near to you. You can include some of these in your signature that you will find in your profile. It will help us geriatrics to remember.