You may want to do a search on "reactive hypoglycemia".
Sounds to me like you definitely have some 'misfiring' going on with your metabolism that doesn't quite fall under the Type 1 or 2 Diabetes conditions. More like you're getting a "reaction" to foods eaten (are they high carb meals by chance?), and your system goes into overdrive pushing out way more insulin than is required.
It's rare, there's not much info about
it, it's hard for docs to diagnose and although it's not classified as diabetes, it is the area of expertise of an endocrinologist. I'm not a doctor and I don't know your full history but, your symptoms (normal A1C but severe reaction to high carb loads), look to indicate it might be something like reactive hypoglycemia.
Hope you get things figured out soon. In the meantime, maybe keeping the carbs to a minimum might help? Wish I could help more