To give an example from my software at work, structural engineering: You make a 3D-model (BIM, Building Information Model) of the steel skeleton of some project. The software can than generate 2D drawings, the blueprints. All beams, colums etc should be labeled in the drawing with the steel profile and quality (if non-standard).

However the software has a terrible label placement algorithm that happily switches around the labels of adjacent elements. And it does so without notice after some changes to the model. That is behavior that can lead to pretty dangerous mistakes.

The reply of the software company: you have to check it anyway. That is why you get paid, right?