Another point. Sometimes it's about the rate of the drop, not the end number.
For instance a diabetic will feel hypoglycemic symptoms if they were to drop from 200 to 180 in 30 minutes because the body senses a very fast drop in glucose.
Even though their glucose is actually high, they will feel low. Even though 75 is borderline, you were on edge because of the sharp drop.
To me this indicates adrenal fatigue/low cortisol. Unless you are shooting out insulin at the wrong times (like a tumor) this would indicate to me that the adrenals can't properly antagonize normal insulin levels and so your sugars plummet.