There's been some cases where "I missed X - there's not enough time to check everything and I missed X". "Well, you should have told us X wasn't checked" or "you should have raised the alarm before". I've been raising it for ... 5-6 months. And the whole point of "I missed something" was... it's a mistake/oversight, not "I intentionally didn't check X".
There are rumors of other developers being interviewed, but no one has come on board. Assuming someone does, I suspect the thinking will be "let's double the previous workload - we have 2 people now".
I'm understanding of the situation, to some degree. Pretty much everyone on the project is 'overworked' in some sense, but they've been hiring and doubling up other positions, just not this one. I've been keeping this pace for 18 months. I scheduled one day off - 2 weeks in advance - because I had to drive someplace. That morning, someone noticed a financial bug that was preventing everything from working. 2 hrs later, from my hotel, I had to connect in and review and fix stuff. It was totally my fault - I missed stuff - but there's just... no getting away from it.
Adding in '5 whys' and other formal review processes on top of this situation borders on insulting.