Finally I think we nailed the printing tolerance measurements! We also changed from white to black ABS filament, which seems to behave more accurately than the white one does.

I added some snap connections and push fittings to the new test piece so we can see if the printer has an accurate repeatability

The new test pieces look even nicer in black!

The snap connections are good enough, I think.
They will probably be better when printed with a higher resolution

The push fitting is tight and nice, just the proper amount of
force is needed to fit the pieces together

I'm also very satisfied with how the motor mount came out, it's a rough test print but the motor and screws fits almost perfectly!

I'm still not sure about the mounting holes for the bottom plate though