Investment in reliability will increase until it exceeds the probable cause of errors, or until someone insists on getting some useful work done.
Every solution breeds new problems.
Enough research will tend to support your conclusions.
A failure will not appear until a unit has passed final inspection.
When working on a project, if you put away a tool that you're certain you're finished with, you will need it instantly.
If your project doesn't work, look for the part that you didn't think was important.