On RCA and how much trust you should put on your co-workers

RCA rule No. 2
DO NOT TRUST YOUR CO-WORKERS!!!
This one is a bit controversial but will take down your MTTR significantly once accepted and normalized.

Assume their good intentions, they really mean well but every problem hypothesis has to be supported by hard evidence – not just statements, because the status quo is often different than expectations.
Your inputs may be coming from a different environment, different software versions and even different projects and it may be simply outdated and, if wrong, they will catch you off guard.
If you’re missing any information about the system you’re troubleshooting, ask for evidence and source of information or, even better – ask how to find it and look for the answers together. This gives you confidence in the information. Make sure you understand what information presented to you represents in the context of your system and your problem at hand.

We’re all human, we all make mistakes. I am wrong too, more often than I’d like to admit. We may have a different and unique perspective on the problem and dealing with software problems is all about the details.