This happened on both my wife's and my 6P. I did a power cycle and there was some walk-thru thing pop up about switches. I'm not sure what it does, but seems to be related to talkback app. Once I just hit next selection on each screen and then finish, it works until next time we lose the rocker volume capability. Definitley a bug, but I'm not really that proficient with Android, so maybe some expert will speak u, but this is what I found it seems to be related to. A work around that's not really very good, but it does work.