I do wonder if this is just a scenario where there's no way to win. The person writing this blog post has exactly the same interview prompt - something went pop when the board was powered up - but they expect candidates to spot subtle things like missing decoupling capacitors that almost certainly aren't the cause of the problem.
Just about every person I've used this prompt on has found the prompted error, and then gone on to find a few more. However, I don't really care about the number of errors you find nearly so much as I do seeing and hearing you reason your way through a new problem.
I don't expect you to find all the issues. (But if you do, then congratulations! I'm gonna try to hire you.) I do expect you to talk to me about your thought process when confronted with a novel issue.
That's what good electrical engineers do. They don't know all the answers - they reason their way through unexpected challenges.
