I was running /e/OS since I got this phone. But it always bothered me that so much stuff was not working. Like Android Auto. That did start working a few weeks ago, and just a few days ago stopped working again.
So I was done. I wanted to go back to stock, so I followed:
- https://support.fairphone.com/hc/en-us/articles/18896094650513-How-to-manually-install-Android-on-your-Fairphone and
- https://support.fairphone.com/hc/en-us/articles/10492476238865-How-to-unlock-and-re-lock-the-bootloader
But after the very last step (all previous steps where fine), I got a “corrupt phone, cannot ever boot” message. I can’t remember the exact wording, it was gone pretty quickly and now the phone does not want to go past “fastboot”. I can use the volume keys to select other options, like recovery, but they all end up returning to this fastboot screen.
I cannot even turn it off, even that returns to fastboot.
So I created a ticket, hoping I can get Fairphone to fix this. But this is not a great experience.
I’ve been in IT for 45 years, I flashed numerous ROMS, from pixels to nexusmod 
But this was the first time when purely following the steps, I got a bricked phone in return 
So there you go, cautionary tale.
Added info:
Downloads | 1 ❱ fastboot oem device-info
(bootloader) Verity mode: true
(bootloader) Device unlocked: false
(bootloader) Device critical unlocked: false
(bootloader) Charger screen enabled: true
OKAY [ 0.002s]
Finished. Total time: 0.002s