Driver updates can introduce bugs as well as fix them. An AMD chipset installer that included a new SATA driver could introduce a bug, for example. The same is true for Windows Updates. It's one of the annoying things about Windows 10 forcing updates; you never really know if your computer is in the same state from month to month. Heck, from hour to hour really. Again, I'm speculating, though. I've seen many instances where a stable overclock became unstable after a short period of time and usually it just gets attributed to the "silicon lottery".