I'm so glad you have much improvement.
Could be one of
at least a few things.
1) Your body could be working on something and adjusting to changed signals (as in repair process)
2) Your body could be sending inappropriate signals due to nerve patterns rearranged during healing
3) Your body could be lacking some other nutrient (calcium, magnesium, other B vitamin, etc?)
4) May be something entirely unrelated
rose