Well, the very first thing that comes to mind is a Methylocobalamin B12 deficiency, common with high
Cobalamin B12 levels.
Cobalamin B12 needs to be converted to its bioactive form Methylocobalamin and under normal circumstances, any excess Cobalamin gets eliminated, as it is water soluble.
In the event of conversion issues, the body sensing the lack of adequate bioactive B12, holds on to Cobalamin B12 stores.
In other words you likely have a functional B12 deficiency, despite your high B12 results.
My suspicion is that it is due to an underlying low Methylation issue, consistent with your symptoms,
which you need to rule out.
Low methylation affects any organ or system in the body.
Detoxification, energy production, neurotransmitters, brain function, gene expression, and a lot more can be negatively affected by low methylation.
The good news now:
If indeed it is a case of low methylation, it is easily corrected by specific supplementation.
Please look it up online and should you have any questions, let me know.
I'm fairly knowledgeable in this area of health, however, my comments are not intended to replace medical advice.
Best wishes,
Niko