> It got me comparing precision machine design to software engineering.
I think the problem is that the failure of physical systems are often caused by random failures, which can be tested for and probabilities determined e.g how long before a bolt breaks. This as opposed to software, which most often fail due to systematic errors and cannot be tested completely.
In precision machine design the failures are typically not statistical (like in fatigue failures) but due to errors of design. E.g. the tool spindle can maintain the desired tolerance when running from a cold start but after several minutes thermal effects cause it to be out of tolerance.
I think the problem is that the failure of physical systems are often caused by random failures, which can be tested for and probabilities determined e.g how long before a bolt breaks. This as opposed to software, which most often fail due to systematic errors and cannot be tested completely.