I had to waste hundreds of hours adjusting all the time until I found out what the problem was: the metric system is not correct.
The points do not connect! I suspect that instead of connecting the center of the points it connects to the RIM of the points.
Millimeters are important in the metric system but SketchUp does not seem to understand that system. I would not be able to design a delicate piece of mechanics! I can’t even design a house without running into problems.
I hope this picture shows and people can see how flawed it is. It shows 0 millimeters while it does NOT connect the two points.