Posted this over on Reddit but got no replies so I'm posting here..
Not sure what's going on, but I usually keep my phone on vibrate during the day, but once I put Lineage on my 6P the volume has been going up the equivalent of one vol. up button press. I don't have any case on my device, and it's happened while sitting next to me. I've put it on vibrate about 3 times just today.
Currently running 14.1 - 20180129 Nightly
I don't know if over time it will go to full blast since I put it back on vibrate after I hear a notification tone.
Odd thing too: I'll hear the alert from the phone speakers even if headphones are plugged in.