I took a moment to check all my settings and adjustments, but they all looked fine, so I did another focus and shot a triple burst. Here is what I got (AF-C set to FOCUS; spot meter; spot focus)
first
second
third
Then a loud metallic CLACK and everything froze. I had to pull the battery...
16 June
Well, I went off today looking forward to putting the new lens through its paces. It did not go well. I was seeing very poor focus, so did some manual fine-tuning, which seemed to improve things a bit, but I was not impressed.