I've just made my first 2 attempts at a 4-strand celtic knot, so I'm probably not the best person to answer this. But, it looks to me like your inserts were not inserted uniformly. The cuts on each side have to be exactly the same depth (I'm assuming that you didn't cut all the way through the blank with each cut), then the inserts have to all be the same size and shape and they have to be inserted the same. Drilling off-center would not cause the problems you have here. My guess is that your cuts into the blank were not deep enough (because a couple of the pieces didn't mate) and maybe the inserts were put in a little out of whack. You can better see how it is all setting up if you use a steeper angle -- maybe 45 degrees or so.
