In your life, you make things, do things, or maybe design things. When you do a good job, your work counts for something. When your efforts have errors or problems, you have just developed a hidden factory.
When you have worked on something that now has an error within it, you must fix the problem. Repairing any item costs time, parts, money, and people. It is a hidden factory because it does not show up in the books.
It is often too costly to take something with an error in it and throw it away. You need to fix whatever is wrong. Included in the repair should be a new process step to remove the possible duplication of that error. If you do not remove the possibility for that error, it will repeat.
What hidden factories do you have within your life and work?
What will you do to remove them?