I put it all in writing monday- then spent 20 minutes answering questions at the job starts with “see the work list” over and over.
Truth is his processing ability is just different. No question.
I faced the same challenge with one of my guys , As a county facilities supervisor I was responsible to "make things happen".
I constantly had to redirect him to the task at hand , he would continually drift from what he was assigned . He was the King of Scope Creep.
If he had a work order to repair a door latch in the courthouse built in 1900 , he would start on the latch and then convince the people in the office that he could refinish all the extensive casework around the doors and windows.
His favorite ploy was to go rogue and convince folks they need to have the jobs done that he wanted to do. However , I had to intervene with the office folks and explain why we couldn't restore everything ! Constant stress.
I needed him to repair the latch , nothing more . I had a small crew , and I had to define the scope of work and the time available for that work.
I totally have lived your present challenge AndyG. I took the same approach you are trying , with mixed results. He would do well for weeks then go off the rails.
Last year I was real sick with type A flu and was off work for 3 days , our manager and him got into an argument, the manager suspended him for a week .
The County Manager heard about the argument and fired him. All while I was away. Hang in there , hopefully your guy catches on to what you need from him and it ends better than my experience.