/e/ FP4 does not transmit voice in phone calls

My new FP4 with /e/OS from Murena does not transmit my voice during phone calls, both out- and in-going. I can hear the other party, but they cannot hear me. Moreover, I hear a strong echo of my own voice. This issue seemed to go away twice, after some fiddling with the settings. The first time, it seemed that changing the Preferred Network Type (to Global) did the job, but it was short-lived. The second time, I switched the permission for the Phone app to use the microphone from Allow to Ask Every Time. Although the phone was NOT asking me for permission to use the microphone, my voice was transmitted for a few days. Then, it went away again, and no changes to the settings were able to restore it. Now I think this problem was coming and going erratically, and my interventions only appeared to mend it by pure coincidence
Worse, I tried to install the original FP OS on this device, but the Fastboot screen says “Device State: Locked”. I have no idea what to do – other than send the phone back to Murena…
Please help if you can.

Regain your privacy! Adopt /e/ the unGoogled mobile OS and online servicesphone

How far did you get with the installation? Did you install FPOS, relock the bootloader and now you get this message or are you unable to install FPOS because of this message?

The mic problem sounds IMHO rather like a HW problem.

I suggest in the first instance …

Week 28, 2022: Development and Testing Updates

I was unable to start the installation. It does not seem to be a HW problem alone, as the microphone works just fine for recordings and for WhatsApp voice calls.

I am sending the phone back for a refund – unfortunately. The support that I have been getting from e foundation was not very helpful. They tell me that they need to test the phone, they are not aware of any other case like this one. For now, I am ordering an FP4 directly from Fairphone, with their standard OS.

In case you still want to install FPOS on the Murena FP4 for testing you should follow the official guide from Fairphone:

This means that you have to enable OEM unlock. Then you have to unlock bootloader and critical partitions (this includes a factory reset so all data on the phone will be deleted).
Then you can execute the installation script for the OS.
But that’s only a rough overview. It’s detailed in the document I’ve mentioned above.

You just shouldn’t relock the bootloader at the end. This might lead to a bricked device and is not needed for testing.