Say a company in my future world has an algorithm that can evaluate and hire job candidates? Would this potentially cause problems like bias or hire people unfairly? Could it also be unreliable?
It certainly could, depending on how it had been programed. Computer code is normally tested before use especially if it is to be used in an important application. However no testing is fool proof and often errors or bugs do not manifest themselves until later when the code is in use. There is an old saying in programming circles that the trouble with making something fool proof is that fools are so ingenious.
It is also possible that it would not if sufficient care had been taken in the design of the code and sufficient testing had been carried out. Critical systems such as plane autopilots and similar often have to undergo particularly gruelling testing before going into operation to prevent or minimise errors. It really depends on the potential problems that might result.
In your example one way to test it would be to run the algorithm in parallel with human reviewers for a while and compare the findings of each.