Even if the instructions don't change in the lifecycle of a particular release, software still fails. Because software is not just the instructions, it’s a combination of the instructions and inputs. At least the output is.
The mentioned bridge failed because it was not designed for the particular input of the ship collision. Same applies for software.
Hardware, time, entropy, users are all inputs. Software and inputs could be the same but some entropy change, or hardware aging could still result in failed output. Isn’t it also failure of the software?
