Puggle Peeing Problem. Can the posse help?

Mr. Puggle received a letter about a puggle with a peeing problem. I will post the entire letter in the comment section. Do you know any puggles that pee in their sleep but don't have accidents at any other time? According to the letter, the vet says there is no medical condition and the trainer says there is no behavioral problem. This family is desperate. See if you can help!

Snip:
We have a 17-month old Puggle. He is trained as a Service Dog and studying to be a Therapy Dog. We have a problem where he is leaking urine on occasions (not all the time) when he is sleeping. We do not believe he is even aware of the leaking.