War story: the hardest bug I ever debugged

I'm seeing a lot of comments saying "only 2 days? must not have been that bad of a bug". Some thoughts here:

At my current day job, our postmortem template asks "Where did we get lucky?" In this instance, the author definitely got lucky that they were working at Google where 1) there were enough users to generate this Heisenbug consistently and 2) that they had direct access to Chrome devs.

Additionally - the author (and his team) triaged, root caused and remediated a JS compiler bug in 2 days. The sheer amount of complexity involved in trying to narrow down where in the browser code this could all be going wrong is staggering. Consider that the reason it took him "only" two days is because he is very, _very_ good at what he does.

I recently realized that one question for me should be, "Did you panic? What was the result of that panic? What caused the panic?"

I had taken down a network, and the device led me down a pathway that required multiple apps and multiple log ins I didn't have to regain access. I panicked and because the network was small, roamed and moved all devices to my backup network.

The following day, under no stress, I realized that my mistake was that I was scanning a QR code 90 degrees off from it's proper orientation. I didn't realize that QR codes had a proper orientation and figured that their corner identifiers handled any orientation. Then it was simple to gain access to that device. I couldn't even replicate the other odd path.