What kind of scan showed misalignment of C-2 ? Was it just treated by a chiro.

It appears there are 2 different issues being discussed.

One is being able to take the deep breath. Jaw problems can make it difficult to open the mouth wide to take a deep breath for a yawn. I dealt with this with a locked TMJ. I was only able to open my mouth a finger width. It took a year to slowly back to 2 1/2 finger widths. My PT did not myofacial release to help the muscles relax. I saw a TMJ specialist dentist and an ENT with expertise in TMJ. He suggested a BOTOX injection to weaken the TMJ muscles.

The second is the ability to finish neurologically. Some can take a deep breath but never get the sense of a yawn. The literature I read did not explain the physical cause of this lack of sensing a completed yawn. A relaxed diaphragm, a relaxing sort of buzz, and related sensations just do not happen at the end of the deep breath. They suggest it is part of anhedonia, a neurological disorder that causes a reduced sense of pleasure.