Sometimes recordings fail stating VOIP error, is this related to only outgoing voip calls or incoming too?
=> Just as you suggested, you should disable the wifi call feature in your phone to fix it.

[002] Solution 3

Phone Dialer> Settings> Calls> Configure IMS Calling> Wi-Fi Calling OFF

Incoming calls work fine,
Outgoing calls only record my voice, no matter short/long "Auto Detect Max Time".

Only works if you manually start outgoing recordings after other party picks-up!  Moto ROM or Oreo issue?

Sometimes recordings fail stating VOIP error, is this related to only outgoing voip calls or incoming too?

Anybody has some other working settings? I've got G6 on Oreo and Boldbeast doesn't record incoming sound.

It's strange if suggested settings in the post #1 above don't work for you.
Can you please:
- record a should recording.
- send the recording to me.
- click "Call Settings - Fix Recording Issues - Ask New Parameters" to send log files to me.
Let me listen to the recording and check the logs, and see what happened in your phone. Thanks.

Please use these settings to record calls:

- Record Mode: 1
- Record Format: MP3
- Tune Audio Route: Group3

Recorded calls are crystal clear in two sides.

UPDATE 1 (Android 8)
=================
Some users said following settings work better:

- Record Mode: 5
- Record Format: MP3
- File Sampling Rate: 44100

Please update Boldbeast Recorder to V11.5 at first.

UPDATE 2 (Android 8)
=================
Moto G6 Plus and Moto G6 Play, some users said "recordings are crystal clear in both sides". However some users said "at first it records the call very well, but after a while (for example after 10 seconds, 100 seconds, or other number of seconds randomly), my voice or the caller's voice becomes very weak in the recording". This problem is exactly the same as Moto G5S, please see this page for more information: https://www.boldbeast.com/forum/topic15 … o-g5s.html

Moto G6, no user met the problem.
Moto G6 Play, some users met the problem, some users not.
Moto G6 Plus, some users met the problem, some users not.

UPDATE 3 (Android 9)
=================
Some Moto G6, Moto G6 Play, Moto G6 Plus users have upgraded to Android 9 Pie.
In some countries Android 9 Pie works great, no root needed, just install Boldbeast Recorder and go.
However in some countries the call recording feature was disabled, you can only record your own voice, the caller's voice is very weak in recordings, no matter what recorder you are using in the market. In this case you should root the phone then this app can fix it perfectly. After root the phone please use these settings to record calls:

- Record Mode: Alsa
- Alsa Device: Auto
- Alsa Bits: 16 Bits
- Alsa Channels: Auto
- Alsa Sampling Rate: Auto
- Fix Recording Issues - Change Audio Controls: Yes

Recordings are loud and clear in both sides.