Reproducibility is a huge issue in academia and in the software engineering world.
As an anecdote, we were trying to reproduce results for a c++ algorithm for which we had the source code, on the same machine, same compiler, only 2 years after its original creation. Impossible. Our best guess is that some os/hw patch / firmware update had an impact on the random number generation, but we never managed to figure out what exactly caused the discrepancies that we were observing.