Highly variant small series that result from modular design approaches are very complex to test:
Have the correct spark plug connector and base feet been installed for the variant? Does the tube connection have the correct orientation? Has the right nameplate been attached? Is the tank cap correct according to the customer request?
The number of product variants increases exponentially with the possible combinations of components. And the higher the number of variants, the less likely an inspector has encountered a particular product variant before. This means the inspector has to adjust to each product that potentially exhibits only a slight variation. In order not to make any mistakes at this point in the production process, the tester will proceed very conscientiously and possibly repeat test steps just to be sure, which significantly slows down the test.