Sorry, i'm not sure at the moment about the modifications i did to the pulseaudio file. Have you tried the one from Real John Galt?

I'll compare them both later. But i think the error could be PA related.

EDIT: They have differences. Just try the one from John.

Interesting read: https://github.com/mer-hybris/pulseaudio-modules-droid

Get debug output from PA with this command:

systemctl-​user stop pulseaudio ; pulseaudio -vvvv -n --file=/etc/pulse/arm_droid_default.pa

Thanks and no worries.
All the problems are definitely audio related. I have figured out the reason why the incoming call was mute, because the ear piece volume was sett to 0. When I used the volume rocker and pumped up the volume, I started to hear. The other issue when the caller didn't hear me was also related because the microphone was off. I toggled to on and started to work this too.
I think the video recording is also related because the camera app is trying to record sound with the video, but something is not configure correctly, therefore it crashes.

I am trying John's .pa file now.
Plus I have spotted a difference between your an my 'hw-settings.ini' file, so I have adopted yours.

What was the difference?

EDIT I'm trying to backport bluez5 at the moment. No luck so far, if i'll get it done, i'll let you know the needed steps.

I have tried this and got the output but not sure how to read. There was no error as I saw. (I started the camera and tried to record a video.)

By the way, do you know how the system knows which .pa file to use?
Currently there are a few .pa files in /etc/pulse:
arm_droid_default.pa
arm_qualcomm_msm_8974_hammerhead_flattened_device_ tree_000b.pa
bluez4_stream_restore.pa
default.pa
system.pa

plus there was my original one that I move away:
arm_msm8974_hammerhead.pa

VideoPlayback=1 was missing from mine

I had the following in mine but were commented out in yours:

#[FmRadio]
#DefaultFrequency=90.0
#InputDevice=input-fm_tuner

#[Audio]
#RecordTopDevice=input-builtin_mic
#RecordBottomDevice=input-builtin_mic
#RecordTopDeviceChannel=left
#RecordBottomDeviceChannel=right

So, I too commented out them.

Bluez5 blackport:
Thank you for doing that.
Why is bluez5 better than buelz4? What is the difference after all?

I forgot to let you know that yesterday I pushed my droid-config-hammerhead, droid-hal-version-hammerhead and droid-hal-hammerhead changes to the github.In case you are interested.

Because of the outcome of my recent camera tests on different Sailfish OS versions, I am not concerned about the video recording in my build anymore.
(I agree with all who says this problem should be fixed but it is kind of a 'nice to have' one. Therefore I'll only try to find a solution once I am done all the other planned tasks or if somebody finds out how to fix .)

Yeah, it would be nice to have video recording too, but I don't use it so much.
I am a bit concerned about the call issues you talked about, does it occur often?

Anyway, thanks a lot!

SFOS 3.2 flashed! First thing I notice, MTP file transfer does not work, it is showing me "Preparing USB mode" but I can see my Nexus on Windows.
Am I missing something?