Maybe it wasn't very clear in my comment but "correctness issues" more-or-less literally mean the instruction's result is incorrect. Like you ask 2*2 and it gives you 0xfff1309f. So depending on how you rely on that result, you may crash. Extending on my examples, bad RSA multiplication means failed authentication. Bad AES construction means encrypting things to garbage, impossible to decrypted by the recipient. So, let's say if you rely on a result from such instruction to do memory references, you're definitely going to crash.