Battery Symbol still indicates charging after unpluging the charger

Neither the factory reset in the OS nor the factory reset in TWRP wipe the phone really completely from my experience. I had my fair share of tries in the past (but perhaps current versions of TWRP do it better? Don’t know.) :wink: .

Unfortunately I’m not familiar with the stock Android recovery which Fairphone OS uses, I never used that. But you can slightly adapt the Fairphone Open OS procedure given here for Open OS’s TWRP recovery …

Slightly adapting means that you need Fairphone OS installation files, not Fairphone Open OS ones, and mind that you need OTA files for installing via TWRP, not files for “manual” installation. OTA files for Fairphone OS are here …

(Be aware that as I read it, you need to install two files in succession this way to get to the current OS version … the “FP2 - Update file of Fairphone OS 1.13.0” file and then the “FP2 - Update file of Fairphone OS 17.12.1 from 1.13.0” file, as the 1.13.0 file is the last complete OTA file given there, even it is called an update, everything else are really just updates from another version. Don’t boot in between, just queue the two files in TWRP for installing and then flash them in one go.)

Anyway, the important part is the complete wipe in TWRP before installing any OS.
If you are not comfortable with flashing the TWRP recovery (even if Fairphone OS should restore its own recovery if you boot the OS directly after installing), you can boot TWRP without flashing it.

If you are more comfortable using fastboot to install the OS, you can leave TWRP be after the wiping, boot into fastboot mode and continue with the standard manual installation given here (download the OS file given there then, OTA files don’t work with this method) …

https://support.fairphone.com/hc/en-us/articles/207914363-Manually-install-Fairphone-OS-for-the-Fairphone-2