(Could guess that one will provoke reactions ;-)) My biggest to date (but not the only one): having received complaints, I figured in 2 days that the culprit i

(Could guess that one will provoke reactions ;-)) My biggest to date (but not the only one): having received complaints, I figured in 2 days that the culprit is the change in the manufacturing-workweek-number of the DDR ICs. It took them several months onsite with people travelling from abroad and with expensive equipment to find the real root cause, and guess what they have found? And I am not even a hardware engineer. How did I do that? Intuition. You need lots of time to develop intuition, much more than 4 years, and once you got it, it saves lots of time and money. I have also seen other experienced engineers do this sort of tricks, and I pity the workplaces where people aren't familiar with this.