In Amber's last few months, I stupidly changed out the litterboxes to a different shape and size. She was a big girl, and had always peed with just her back half in the box and her front feet outside. After the change, even though the change was to a larger box, she somehow got really confused and, ever afterwards, turned herself around so that her front was inside the box, and her back half outside. With the predictable results.
Anyway, the one useful bit of info I can offer from that experience is that setting up puppy pads around litter boxes works really really well for simplifying cleanup and cutting down on aggravation, especially in early mornings when you have to go to work!
I do hope it's also just a little behavioral quirk and not the UTI for Buzzy. He is looking good!