I've now built 2 necks and just finishing the 3rd. On both the first 2 I found that over a period of a few months, the seamless transition between the neck wood and fretboard there's a very slight ridge which formed you can feel. In other words there's been differential expansion/ contraction of the 2 types of wood. The neck was finished to 2000 grit, neck is oiled I sanded it flat again on my first neck, so all smooth and seamless again, but I not sure if this will happen over time again and more importantly, how do I prevent this from happening? Also, is this a common occurrence?