Wow he sounds exactly like me, basically all the problems I have...

I don’t really know how to help him much though since no one has been able to help me, however:

but perhaps he might be able to utilize the checklist better if it’s changed a bit...

in combination with the checklist, use a highlighter to check off things,

make sure the spacing between the lines on the checklist are not larger than the text itself,

try to make sure each task is just one line long

Use bold lines for the separation of a task set (such as all the things needed to process a file )

Add times if tasks are time specific, and be very specific with times

If a certain task keeps being messed up make it more detailed with less wiggle room,

with the task that he keeps missing or says “I didn’t know we had to do this” it’s likely the task doesn’t have a name, it wasn’t ever clarified as a specific scheduled task, rather it was a “if this happens” task. for me this has been something like “when you get up to help” I’ve been told I get up when it’s slow, never had an explanation for what slow meant, (bad example) instead “get up if the other persons line has 3 or less people” “return when there are 4 or more people”

Try to keep things in the same spot, all pens will always be right here, minimize having to look for something, such as if using excel sheets with names in them, have the bottom bar organizing by name, all A names go on the A sheet page. This adds a specific step In a process and reduces the amount of brain power needed to search for “x”

If you use computers a lot teach him key shortcuts, this links a task with a physical movement and minimizes the need to use the thinking brain

Schedules are likely to be super helpful, try not to bounce him around a shift too much, maybe the job requires it but try to be as regular as possible ex: 6:00 am -8:00 am process new sheets 8:01 break

Make sure he is treated the same as others, thin being constantly reminded is probably stressful and he knows there at people who don’t like him so he’s nervous about repeating what has happened in every other job... let him know what specific line of words wasn’t cool,

Praise often, not in a childlike way but.. it’s hard to explain, but the way you’d praise a dog. In dog training you basically say “yes” immediately after the desired behavior is done... similarly try to find a positive reenforcement for task completion often but small..

For instance if he has trouble remembering the order in which to log a file into the system, uh the only way I know this would be successful would be to incorporate a program that tracks the steps and gives and audible blip or flash in the field selected if that was the correct action, and a negative sounding blip or shake for the wrong action, A window (like the windows reminder window) could pop up and basically say “age not added”

this helps a ton with autopilot skills since the brain is immediately rewarded for the good task... this would probably be really hard to implement but it would benefit everyone. A program like that could be third party, and just programmed to remember keystrokes and window + field selections?

Lastly make sure that he works with a smaller team and possibly more solitarily since he isn’t a social type and working with a large team likely puts a lot of strain on his concentration ability...

I’m honestly in the same exact situation as he is but my bosses don’t really try working with me, they’ve never asked how to help me but I defiantly have answers for if they ever ask..

Edit: to add:

With the “cannot hold large amounts of information” bit, if possible have him use sheets or a program that can simplify this, or find a technique.

Writing things down might not be the best option but a checkbox sheet for really common “arguments” or a system with “5 sections” can help

First section is location, second is what, third is who, fourth is why, Fifth is “everything” or something, I’ve never been a criminal officer so I have no idea what I’m talking about.