In the first image, that of the coin, there are spheres with a diameter of 0.9 mm and I printed. I'm sure! While in the other images of the letters are 3mm and not print at all. It 'really strange.
Now I did a test with these L. As you can see the size is 14.5 x3x2mm. In the x-ray view there are no errors but still does not print correctly.
http://i62.tinypic.com/35bwok4.jpg
http://i58.tinypic.com/izuxxk.jpg
http://i62.tinypic.com/j13w4x.jpg