It looks like the in call volume bug affecting some devices is caused by libsecril-client.so. Replacing it with the one from lineage-14.1-20170712-nigthly-i9300 fixes it on the latest nigthlys. Looking in the changelog I think there's...
It looks like some devices have problem with SELinux. Call audio it very high and trying to switch it returns-
12-07 08:51:40.108 2553-2899/com.android.systemui I/vol.Events: writeEvent active_stream_changed STREAM_VOICE_CALL
To save you time - the lineage-14.1-20170830-nightly is still affected by the incall volume bug.
It looks like after 20170712 NIGHTLY some devices are affected again with in call volume stuck at max but this time the cause is not the SELinux. It isn't and Baseband related. Switching to XXUGMK6 didn't fix it. Is it possible one of...