What your B12 levels are. The actual numbers.

When the auditory nerves act up, it can be similar to optic neuritis which can be due to autoimmune issues or low B12.

Most of the diagnoses I see for vestibular issues are "viral".
This is the typical cop-out when answers are not evident.

I myself have "attacks" in my left ear. I have had several of these over the past 60 yrs. Some that have been severe and put me in bed in one position for days! When I had testing for vestibular function long ago, they told me it was most likely due to a head injury (abuse when I was a child) or measles. The test was very low in that ear, but I do have at least 50% hearing there, and poor balance (esp when eyes are closed) still. When I was very hypothyroid I lost some hearing but that has come back with thyroid hormone treatment. I have only had one vertigo attack since my thyroid was "fixed"...and that was due to Glucophage..a drug. So that sort of tells me that my vertigo is somehow connected to the hypothyroid. I also have damage on the left lobe of the thyroid as well. (coincidence?)

When I used Glucophage for insulin resistance I developed a severe attack (I think was due to acidosis), and had to discontinue the drug.

The ears are very sensitive to fluid accumulation. This is called benign serous otitis media when not infected. I was given that diagnosis too. I have had my ears drained with a needle once (this was a horrible experience) and to this day, I get seepage of the fluid if I don't take antihistamines regularly. I tend to get dizzy/lightheaded when that pressure builds. I find Guaifenesin helpful in draining it.
When fluid builds in the middle ear it presses on the eardrum which then causes dizziness/vertigo.

I think that there are manual causes of dizziness.
Did you have an nystagmagram (where they blow warm air into the ear and measure with electrodes the response)?
Even with that test, they told me I should be deaf in my left ear and I am not. So I have wondered for most of my life how accurate the testing really is. I had a normal caloric response in the right ear...it is only the left that gives me grief.

Basically I don't think medicine understands everything about ear functions yet. So the only thing YOU can do is cover the nutritional bases, and supplement those things that help nerve functions.
B12
folic acid
fishoil
magnesium
B6
etc.

Do you have neuropathies elsewhere? Or only the ears?