Don't know if you know who Susan Garrett is (she's a world famous dog trainer and agility star) but I recently subscribed to a year long, online training "thing" with her. One technique that she uses for puppies is to train in her bathroom. It's about the most boring environment she could possibly think of, not to mention it's pretty small so there isn't a lot of "exploration" space. This allows the pup to not be distracted by the environment. As the dog gains focus, confidence, and skill- she will move to more distracting environments. If the dog fails in that environment- it's back to the bathroom.
You're right- seems totally obvious. But I wouldn't have thought of it either unless I had seen her do it...
Glad I could help! I think you will find success with such an environment switch...
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