I have some experience with healthcare software and the core of it is pretty simple. The 2 biggest sources of unknowns however are quirks of the existing system

I have some experience with healthcare software and the core of it is pretty simple. The 2 biggest sources of unknowns however are quirks of the existing system and edge cases in human processes. Neither can be accurately estimated for because complex systems are never documented in enough detail and even humans who have been using them for decades overlook and misremember things. I’m sure this is the case in any complex enough business system as well.