Yes! But they can behave deterministically for any kind of input data. Of course they interact with the outside world, and I'm not saying you can't have errors, I'm saying they're not random and driven by god's will, they're programmed explicitly.
In my first class of Software Engineering, I was taught that software is designed for changes. Even if software the fully deterministic, it interfaces with a world that is constantly changing: requirements change, customers change, political systems change.
What does that have to do with fallability of software?
Unless the chip has a bug or manufacturing error; I've worked with several fleets where small numbers of chips had stochastic errors. I doubt there is any fleet which does not periodically have some level of corruption, which typically goes unnoticed unless you have engineers paying close attention and some level of verification.