mobile

I was using 5.0.1, with stock bootloader, stock recovery, actually stock everything except SuperSU added.
I downloaded the 5.1 image from Google, and tried flashing it:
fastboot flash bootloader bootloader-mako-makoz30f.img
fastboot reboot-bootloader
fastboot flash radio radio-mako-m9615a-cefwmazm-2.0.1701.06.img
fastboot reboot-bootloader
fastboot update image-occam-lmy47o.zip

Got some missing sig errors, and "failed to allocate xxxxxxxxx bytes" error. Thus after searching for more information I ended up unpacking image-occam-lmy47o.zip and running:
fastboot flash boot boot.img
fastboot flash recovery recovery.img
fastboot flash system system.img
fastboot flash cache cache.img

Then rebooted. The result is an endless boot animation, regardless of anything I try. Tried restoring my TWRP backup, reflashing 5.1, reflashing 5.0.1, always the same. Last logcat line at boot:
E/kickstart( 233): Sahara protocol completed

Then it's just stuck there. For minutes. For tens of minutes. Looks like forever. Anyone else ever seen this problem, and happens to have a solution? (Preferably without losing my data)