i recently turned my HTC One into a Google Play Edition with the Conversion RUU Zips and just wanted to get back to WWE Stock and used a RUU from HTC for this, but everytime and on multiple devices I was getting the error:
"fastboot-htc.exe has stopped working..." and the whole program just crashed. (the phone wasnt bricked, even after many times.)
at the Beginning of flashing the RUU.
I solved it by flashing a Combined TWRP Custom Firmware Package from this thread (use Combined, NoWipe ZIP's with same version of ruu) and then repeat the RUU.. and this time it worked. (List of all Firmware)
I select the version that the RUU was going to flash (for example at mine: 4.19.401.9 for the same RUU version)
[* also with unlocked bootloader and S-OFF, no need to change that!]
Maybe the RUU doesnt like the GPE Firmware, but this was the solution.