I agree with Hockey. The twist and pop is often way too aggressive. I'm not impressed with a 'functional neurologist' who uses twist and pop.

Do you have access to an upper cervical chiro who uses gentle techniques on the neck ?

An unstable neck can be fine until one bad night sleeping in bad posture or a quick turn of the head or even a sneeze. It takes weeks and even months for the ligaments to strengthen and tighten to stabilize the upper neck.

Prolotherapy will not help if the neck is not aligned and stabilized so the ligaments can heal to support a proper position.

How do you support your head when you sleep ? What position do you sleep in ?