I don’t have time to explain and clarify my comment right now, but I will after April 15th...
Allow me to explain that the vestibular function works through the cerebellum and is the same area of the brain that is being tested when a police officer does a field sobriety test. It is also the reason why alcohol is used by many as an escape from emotional troubling memories. There are more dendrites in that portion of the brain than the rest of the brain combined.
The cerebellum is also the brain processing location for proprioception or balance function.
I have also found that vagus nerve stimulation causes individuals to block function in the cerebellum.
It is very logical that an individual with a balance disorder has a fear of heights. I wouldn’t classify this as a phobia as a phobia is unjustified fear. This fear is justified.
Stress however can indeed make these symptoms become more acute or begin to show sooner than it might have otherwise. This is simply because with cerebellum/Vestibular disorders the brain is in an almost constant compensation/correction mode correcting the incorrect sensory system. The more stresses you add good or bad the more overtaxed the brain becomes.