Ring Volume greyed out?

[wetherb67]

For the third time, after putting my phone in vibrate mode, now the area for Ring volume is greyed out and is not usable. Anyone have this problem? After a restart it seems to work fine.

 

[Mark Murphy3699]

I'm having the same problem with my Moto X Pure edition 2015

 

[JaneBF13]

Same problem, also a Moto X, ever since last update. Doesn't become active/adjustable again until after reboot. Would like a fix for this please!