This happened not to long ago my jailbroken phone. Basically I was just texting my friends and I turned up the ringer volume and the picture of the bell wasn't there I didn't think much of it until my phone froze up and didn't respond to anything. I watched it and slowly it icons started to disappear the phone then went into safe mode and became responsive again I restored the phone and everything was fine. I have no idea what it was I have changed my passwords incase it was some malware taking my passwords and deleting my phone. But I have no idea what happened I can't find anything about it and I don't want to jailbreak again if someone can tell me what that was maybe I will jailbreak again. Thanks!
...I would not be jail breaking again anytime soon either. Anyway, hopefully somebody with jailbreak knowledge can explain what happened on your device specifically.
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