Flash SMS
Why would you want messages that immediately appear on your main screen and don't obey the settings you have for SMS? Seems one good way to fix this would be to disable flash SMS capability in the Nexus.
A Romanian security researcher has published a vulnerability that allows someone to crash a remote Nexus 4 or Nexus 5 phone – by sending them a crafted “Class 0” text message. Instead of falling into a user's inbox and waiting for someone to read the message, a Class 0 or “flash message” pops up immediately as a message window …
According to Wikipedia, Flash SMS is used for emergency broadcasts, i.e. "you're about to be wiped out by a tornado, good luck!".
Looking in Settings > More... under Wireless and Networks > Mobile broadcasts, there is options to choose which to display and a global option to disable them all. It also has an audio option so not sure if this is the same thing.
The screenshot also shows the Messaging app snuffing it. This has been replaced with Hangouts on the N5, is that too affected? Hangouts can optionally replace the Messaging app on the N4 too.
More info please Reg.
I know from experience that the bug doesn't affect CyanogenMod. This is because they enabled flash messages in nightly builds earlier this year, and it caused phones in Europe and perhaps elsewhere to be swamped by network messages - but without crashing or losing connectivity. It turns out that these messages are used for things other than emergency notifications outside of the US, and were previously ignored. My phone was getting somewhere in the region of 120 flash messages a day, about three of four each time I moved from one broadcast cell to another, and some numpty developer had removed the option to globally ignore the annoying buggers.
Not playing an audio sound is hardly the problem, personally I wouldn't want an audio alert every time some random person decides to send a class 0 SMS to me because they think its important. What is the issue here is that the applications that handle SMS need to handle large volumes correctly without crashing, im astounded really that the primary function of the application, receiving an SMS can not handle load, i mean, was no load testing done on the application at all to ensure that it can cope with any number of SMS being fired at it? Total idiocy.