I think most people might be on this boat.Ill-compensated due to migraines. How long has it been for you on the MAV train ?
If you had vestibular neuritis or any vestibular trauma and got VNG soon enough you will see the defecit. You wait for more than 6 months the deficit becomes less pronounced as you partially compensate.
VEMP only measures the ear and takes the brain out of the equation and it clearly shows vestibular damage. I had mine done 3 times to see the pattern from the noise.
In my case there was amplitude asymmetry in my cervical VEMP. It could mean hydrops or some VN related damage. Clearly my brain is pending some compensation.
The good news is these kind of cases get better in the long term. I have spoken to one person who definitely had VN and was suffering for a long time. 2.5 years out now and he is 100%. He finally compensated and reached a baseline.