[Nexus 5 Q&A, Help & Troubleshooting] chairshot215:
I have had a few issues with latest versions of CM.

First was errors received during the flash process. Was able to get past this a number of ways.

Change bootloader version in update script.

removed bootloader version check line altogether from the script .

Edit line in source for my current bootloader and compiling myself.

This was all find and dandy but with every one of the above mentioned changes to either flash an official nightly or one compiled myself after flashing has gone through without error I am stuck on the "Google" logo after rebooting into system. Have done a quick search and have seen a number of posts like the one mentioned above that after getting past flash errors by modifying update script or in the above case had probably worked because older script was from an update.zip created before the bootloader check had been added by CM after the flash was successful no additional issues had been experienced.

So far I have tried a number of different update.zip's from flashing a number of official nightly zips to compiling my own nightly and even going back and flashing older CM-12 versions either still on SD card or PC that I have flashed in the past without issue and depending on age flash currently without any bootloader version edits as had been created or downloaded before the check had been added and still nothing will go past the "Google" logo.

"

Have also changed versions of TWRP and at one point had seen two versions with one for caf that I do not see as I no longer see any versions on the TWRP website just link to install the TWRP Manager app but in my quick reads had seen that it had only addressed the bootloader issue but now not sure as it had disappeared once I returned for more info and to download.

I do not have any problems installing AOSP Roms as compiled, flashed and running 5.1.0_r3 for a few days now and have no issue in restoring cm12 created nandroids even though flashing the zip from which the nandroid was created results in a permanent stop on the "Google" logo the nandroid restores and boots up just fine. Also had yesterday gave cm another try as had seen a commit in hammerhead device listing my current bootloader and "LMY41I" Build Number but still "Google" logo.

Should also probably mention I fastboot flashed the image for first "LMY47D" image and then later the "LMY47I" images. After each image flash would first thing fastboot flash twrp and create a nandroid backup before doing anything but would then flash supersu reboot system and set up everything before creating a second nandroid of each. Not sure how this would effect my current cm issue but thought worth noting because am obviously confused so what I think may be related in any way can be thrown out the window . Otherwise have not seen anything helpful in researching and have even considered flashing the bootloader taken from the 5.0.1 factory image as problems began after flashing 5.1.0 "LMY47D" factory image.

So far I have tried a number of different update.zip's from flashing a number of official nightly zips to compiling my own nightly and even going back and flashing older CM-12 versions either still on sd card or PC that I have flashed in the past without issue and depending on age flash currently without any bootloader version edits as had been created or downloaded before the check had been added and still nothing will go past the "google" logo.

"

Have also changed versions of TWRP and at one point had seen two versions with one for caf that I do not see as I no longer see any versions on the TWRP website just link to install the TWRP Manager app but in my quick reads had seen that it had only addressed the bootloader issue but now not sure as it had disappeared once I returned for more info and to download.

I do not have any problems installing AOSP Roms as compiled, flashed and running 5.1.0_r3 for a few days now and have no issue in restoring cm12 created nandroids even though flashing the zip from which the nandroid was created results in a permanent stop on the "google" logo the nandroid restores and boots up just fine. Also had yesterday gave cm another try as had seen a commit in hammerhead device listing my current bootloader and "LMY41I" Build Number but still "google" logo.

Should also probably mention I fastboot flashed the image for first "LMY47D" image and then later the "LMY47I" images. After each image flash would first thing fastboot flash twrp and create a nandroid backup before doing anything but would then flash supersu reboot system and set up everything before creating a second nandroid of each. Not sure how this would effect my current cm issue but thought worth noting because am obviously confused so what I think may be related in any way can be thrown out the window . Otherwise have not seen anything helpful in researching and have even considered flashing the bootloader taken from the 5.0.1 factory image as problems began after flashing 5.1.0 "LMY47D" factory image.