O dear… Is it him again? Why can he not understand how this system works…!
What are you correcting:
Before jumping to conclusions, you need to check how this person was declared competent for the job. Where was he trained and was that up to date? Did he have the right tools, materials, instructions, enough time etc?
If the person is working in a situation which is beyond his competence, mistakes, slips and lapses are waiting to happen.
If slips and lapses show a consistent trend, you could indeed question competence for this type of job. If mistakes are consistent, more training / coaching is justified. At the same time, you should look at how the organization creates the situation whereby people who are not competent to the task are put at work. Here you should look at the planning proces, the instructions management gives and perhaps bigger or personal consequences that managers are trying to avoid with this situation ("He was the only person I had so I let him do the job otherwise I would have looked bad").
If it turns out that the person in question refuses to take input and integrate learning that is the key issue to be addressed. In a just culture everybody can make mistakes, but refusing to share, learn and improve are a real no-go.
How are you correcting
You should really go into these situations with the intention of discovering the pattern. If the organization stops learning things are wilfully put at risk. Find the pattern that makes this situation recur, and share the learnings without blame.
However, when it turns out the the repeating event is caused by somebody wilfully not changing his or her ways, you should consider taking this person out of harm's wasy by removing him or her out of the proces until a change has happened.
Manager should be trained on recognizing and correcting these patterns.