Trying to fix naturally bricked M7

Hi,

I'm trying to fix my friend's bricked HTC One M7. It's completely stock but won't boot (stuck on white HTC screen). On rare occassion I've seen it boot to the white Beats screen and just once it got to "starting apps" after a very long time (a couple of hours?) and hung there. Booting to bootloader, fastboot and getting into recovery works. I've tried fastboot erase cache, and a "factory reset" both from bootloader and from recovery. Factory reset from bootloader just reboots the phone to the white HTC screen. Factory reset from recovery seems to finish (after a long time) but the problem of being stuck on the white screen after rebooting isn't solved. I downloaded the appropriate RUU but fastboot oem rebootRUU only reboots me to the white HTC screen, not the black one as expected, so I can't continue with flashing RUU.

fastboot getvar all:

version: 0.5
version-bootloader: 1.61.0000
version-baseband: 4T.35.3218.16
version-cpld: None
version-microp: None
version-main: 7.17.661.7
version-misc: PVT SHIP S-ON
serialno: ***************
imei: ***************
meid: 00000000000000
product: m7_ul
platform: HBOOT-8064
modelid: PN0712000
cidnum: TELUS001
battery-status: good
battery-voltage: 4265mV
partition-layout: Generic
security: on
build-mode: SHIP
boot-mode: FASTBOOT
commitno-bootloader: dirty-eff4f609
hbootpreupdate: 11
gencheckpt: 0

Thoughts? Please help me make this a phone again!