Potter's two non-touchbacks, IIRC, came towards the end of the 4th preseason game against the Lions. It was indoors, so weather change was not a factor. However, the Bills had scored several times in the latter half of the game - in fact the last preseason game was the only game in which the Bills had scored much at all.
I'm wondering if Potter's leg was getting tired by the end of that game. He would have had to kick it off 5 or 6 times (maybe even a 7th, I couldn't find the complete box score), and nearly all were in the second half. That was far more often than in any other preseason game the Bills played.
Maybe his leg was getting tired by that time. I think that's one aspect of Potter's game that deserves watching. What do you think?