Not sure what you mean by “popping out sideways”.  Driving with a hammer, they
went right in, but I had to be careful to drive it straight. It was easy to
bring back to plumb, but easy to get out of plumb a little.  That is what leaves
a bit of a wonky surface on the wood.  Also, the hammered ones had more of a bow
along the length, but once we pressed them through smoothly, they look great.

Ed