Not so much inconsistent - even the brand names have been guilty of being inconsistent - but different from each other. It's the binders and fillers that most people have problems with and they are going to be different among the drugs. You could do fine with one generic but have a reaction to another. If you do find that a generic works for you ask the pharmacists to make note which it is and get that one every time; often pharmacies will get whichever generic is cheapest or most readily available, so you're not guaranteed the same one each time you refill your script.

HypoT tend to be very sensitive and have more allergic reactions than the general population which is why this is so important and can be such a PITA.