Teeth chattering, called 'chuddering', is perfectly normal in a Basenji. Boys do it if they scent a female in season, and the girls do it too, around the mating time of year.
When my boys did it - I knew that either there was a seasonable bitch in the village or it was time to segregate the sexes to avoid any ooops mating or unnecessary fights between the boys.
It would seem your vet has never come across a Basenji before. That should sound warning bells for you. Basenjis need vets who know the breed cos there are all sorts of things to avoid / look for when treating them.
For example, does your vet know that Basenjis clean themselves like cats and therefore no external preparation which is not safe to ingest should ever be used ?
The yawning could be over heated atmosphere - central heating too high. Try to educate your vet or find another one and get him / her to keep an eye on things but personally, I wouldn't worry. I'd look around the area you live in and see if there is a bitch of any breed heavily in season.
Good luck