Hmm, i seem to have found an issue (or made a mistake) so that i can't fit a piece properly.
In book 2, on page 17 you should place a technic plate over a pin on an axle. This however does not fit on my build:
I removed some of the build to be able to take pictures. On the image below you see that i can't click the plate down (it bends when i do this, and naturally it springs back up).
The cause is that the axle is to long, so that the pin does not have enough room (i lightened up the spot as it was a bit dark).
I removed the coupling bit so you can really see that it's not a problem of pushing the axles far enough into the coupling.
So the only solution for now, is to remove the pin and replace it with an 2L axle (i just used the pin temporarily).
Did i do something wrong, or is this a real issue (or should i force the plate on, bending it)?