Hiya
How old is your pup? It's possible that if he is quite young, new things are just, well, too
new and interesting for him to be able to control himself. When I took my Milly to training classes, the trainer (a highly respected Kennel Club trainer) informed me there was little point in trying to teach her to stay in an interesting and exciting place "this side of Christmas", because she was just too excited about life in general to keep her bottom on the floor.
It's possible that perhaps Thor is suffering from highly-excitable-adolescent-doggy syndrome? And maybe time will do the trick?