Though they were super smart and a rapid typist they were also dyslexic. To make it worse, they would never take responsibility for any mistakes resulting from their failure to double-check the figures entered into the software they needed to run. As a result, we were constantly forced to rerun processes they had worked on because the person never reviewed the parameters they entered into the processing modules before running the jobs. Very simple mistakes like entering 1005 instead of 1500 would cost us a day or more rerunning jobs. It took me weeks to detect the pattern of failures and link them conclusively to this individual since other jobs by other people I supervised also failed but for different reasons.
Once I saw the problem and could easily document the issue I took a few moments to sit with them privately to show what I had found and made the recommendation that they should double-check everything they typed before submitting the jobs so that we could eliminate that class of failures. This person was adamant that I had to be wrong and that they were a perfect typist and somehow someone else was responsible.
Try as I might I could not get them to adopt a simple review-before-submit plan so, since they were a valuable team member who didn't need to lose their job during a period where good jobs were not easy to find, after consulting with my superiors it became my job to review everything they submitted, correct any input parameter fat-fingers or dyslexic inputs, and resubmit those jobs so that we could eliminate those failures.
It was easy enough to do so we made it work and they were never informed I was bird-dogging their work so closely. They remained a valued member of the team until one day they put in their notice.
They had been applying for any positions anywhere that would allow them to use their programming skills on problems that a physicist might find challenging. They had been offered and had accepted a position as a programmer with Raytheon working on missile guidance systems. After their exit, we joked that one day we would hear about a fat-finger mistake sending a missile to an unintended location.
This person was not connected at all to this event since their work with Raytheon was several years after this event occurred (SSC shuttered in 1993). I have no idea what they worked on while there but I hope that someone noticed the issue and insured that two sets of eyes hit everything they typed. Those were the days.