I expect that overwork of the day shift is the far more likely theory. Elon Musk expects employees to work 80-100 hours a week. I've done 100 hour weeks before and I made a lot more mistakes than when I've worked 40.
I have roughly the same experience. At the beginning I am sustained by the urge to get something done so I stop noticing warning signals and when I finally notice it is exactly because of inability to focus and because of mistakes I make.