Disturbing problem with DND

Mar 22, 2016
For a number of weeks I have had a problem which has meant that some calls / messages are not received / notified in time. The DND / Silent Setting keeps getting activated, several times a day. I have changed the Sound Settings to every option, many times, but with no effect.The regular option works for a while but then without warning it is switched to DND / Silent. I have now got the habit of pressing the audio button many times a day, which works up to a point but sometimes is missed. How do I get rid of the unwanted behaviour?
try it in safe mode. this will prevent any 3rd party apps from running. it will let you know if this is an app issue that is causing DND to keep switching on. if it still happens in safe mode then i would consider doing a factory reset and hopefully that will fix the issue.
Thankyou all for your replies. At the moment the issue seems to have gone away --- I cannot be sure yet, but what is displayed when I open the relevant Settings page has changed, and so far the sound settings are all 'on'.

I tried to follow the SafeMode suggestion but it seems my phone is one of the few which do not support the 'standard' procedure for SafeMode for getting into it. Can you advise on this please?

I have another issue regarding Casting the display but will open another post for that.
Hello --- sorry to be so long to reply / update ---- I have been struggling with a major Windows PC problem, now largely resolved. I was wrong in saying the DND problem was solved, it still continues to switch on DND erratically. I will ask about Safe Mode and another issue in new threads