Oh boy... My Alex does the same thing! Around the house, he is outgoing, obedient, playful and silly. Outside during our walks, on occasion and for no apparent reason, he will sometimes just put on this brakes. What is his body language? Just picture a big, strong stubborn mule. He wears a determined look on his face and stiffens his body. Trust me, there is no way to budge his 90+ pound majesty when he gets like this.
I have tried pushing, pulling, cajoling, pleading, treating, enthusing, threatening, promising, sprinting and every other kind of "ing" I can think of - all with defeating results. My other Grey waits patiently as all three of us stand like silly-looking statues on the sidewalk, for many minutes, waiting for Alex's spell to pass. (Sigh.)
Is he playing me? Definitely. Alex never locks up with my husband, whom he has the biggest "man-crush" on. I have had other people pack-walk with us, and Alex locks up indiscrimInately with everyone. Everyone, except with hubby that is. Alex wouldn't dream of ever disappointing him. What in the world is going on in that canine brain of his?