We used to have an employee like that too. You could give him exactly one task at a time. Any more than that, and he would get overloaded and nothing would get done. And even then, the one task usually had to be double-checked, because there was a good chance he would do it wrong. Even when it was something we did every day, and that he had been shown multiple times.

He was the embodiment of “the lights are on but nobody is home.” He was awake and seemingly alert… But holy shit, that is a very big sliding scale. Oftentimes when talking to him, you legitimately got the impression that he was zoned out like a driver turning their brain off during their commute.

He quit to become a middle school teacher. No clue how he is doing now, but we made lots of jokes about his middle schoolers being smarter than him when he left.