Here is the latest log. I got a call on 2016-08-31 at around 06:31 UTC, there was no ringtone (TBH it rang for a fraction of a second and stopped abruptly. I had the phone just in front of me, so I could observe this behaviour. Otherwise I couldn't possibly have realised this.). Got another at around 06:46 UTC, this time rang fine.
Here is the latest log. I got a call on 2016-08-31 at around 06:31 UTC, there was no ringtone (TBH it rang for a fraction of a second and stopped abruptly. I had the phone just in front of me, so I could observe this behaviour. Otherwise I couldn't possibly have realised this.). Got another at around 06:46 UTC, this time rang fine.