Unable to relock the bootloader

Device: Fairphone 5
Installed OS version: 4.9-20240130

Hey, I just bought a fairphone 5 and decided to install iodé OS on it.

I followed this official guide:

The automatic installer weirdly never worked for me, since it loses connection to the device when rebooting into fastboot.

The manual way works just fine for me.

What I encountered after trying to relock the bootloader is similar to the following post:

Behaviour after Installation:

Without locking the bootloader:
It shows the warning, that the bootloader is still unlocked.
Then it continues to boot into iodé OS just fine.
When checking for OEM unlock, OEM unlock is active.

It seems I can use it just fine.

With locking the bootloader:
It shows a message where it says “<!>
Your device is corrupt. It can’t be trusted and will not boot”

When I re-unlock the bootloader and go through the whole process and after installation DONT relock the bootloader, the behaviour is the same as mentioned above.

I did not use the command “flashing unlock critical” and am not planning to do it.

My Questions are the following:

  1. I don’t know if this bricks my device in the future, so is there a way to create a backup, so I can load it back when everything goes downhill?

  2. You can order the Fairphone 5 with iodé OS preinstalled. I assume, that those devices don’t have this issue. If I’m correct: How are the iodé employees achieve it?

Thanks in Advance