My root cause analysis course has a major emphasis on the fact that it is our thinking process (as opposed to computers or other tools) that has the most significant impact on our success in problem solving.  There are various approaches that are more or less effective at guiding RCA, but behind them are cognitive biases that we are not likely to be aware of which can also subvert the analysis.  Here are just a few:

• Anchoring bias - If the problem used to be a lot more or less prevalent, we use this as a benchmark to decide whether or not it is important now.  In reality, we should consider the larger picture, such as frequency, cost, risk, and strategic impact when we're deciding whether or not we should work on a particular problem.
• Recency effect - If the problem has occurred in the past we often automatically assume that it's caused by the same thing again, also there may be absolutely no rationale to support it.  This can cause us to waste a lot of time and energy that would be better spent taking a more systemic view of the problem.
• Confirmation bias - There is a tendency for us to latch onto particular causes we believe to be more likely, and to try to provide they are the culprits.  What we often forget is that we should also look for data that may prove that our theory is wrong (but who wants to be wrong?).
• Overuse of heuristics - The more experience we have with the technology involved in the problem the more quickly we'll rush to judgement about causes (or even solutions ... skipping over causes!).