The Ringo built correctly and all works. However, in attaching the case, the longer M screws (the bottom ones) don’t reach the top brass spacers in several places so the case does not hold together. I have been very careful to use the correct screws at all locations but most don’t reach far enough to screw into the brass spacer.
What can I do?
Solved.
The brass spacers appear to be two different sizes (not very obvious). But put all the shorter spacers on the longer screws (on the back) and then the screws are left long enough to reach the longer brass spacers from the top.
Hey,
Yes, that was the issue! They are very similar yet make the whole building process quite different. I can only recommend you to read the manual a bit more careful next time! 
If you have any other issues, feel free to write. 
Cheers,
Robert