It seems "PU Fail" happens when you try to install it after already successfully installing it once. Makes sense.... firmware stays put, as does the radio, after wiping and installing new ROM's etc. It makes sense that the partition update would fail if you've already flashed it successfully once. Android is just telling you...no need to update.
As a test, I simply ran it again.....I was able to get the "pu fail".
I guess some people are getting that even on the first attempt? My first attempt updated without any issue....second try, for ****es and giggles...fail
In any event, THANKS to the OP! Good work!