My SPH-L720T is running rooted L720TVPUAMK5. I've had the phone about 15 months (purchased new from Ting).
It works fine except about on 10% of the calls (incoming and outgoing) it locks up hard. Except for incoming and outgoing calls the device has NEVER locked up. Its been doing this for as long as I have owned it.
When I go to answer a call (I'm not using Skype, Google Voice or Wi-Fi calling or anything like that), the screen locks mid swipe and stays frozen. I cannot hear the calling party, and they cannot hear me.
When making an outgoing call, when malfunctions all seems normal except that I never hear the sound that indicates the phone I'm calling to is ringing. At that point the screen stays frozen.
The device appeared to me to be unresponsive to all physical buttons. Previously, at this point I would pull the battery. I eventually corrupted the MicroSD card, requiring a format.
After that, I learned that holding the power button does bring up the reboot dialog. But it takes a lot longer than normal to come up. And then after touching reboot or shutdown the device takes about three minutes to shut down or begin the reboot. That was so long that I had thought it was hopelessly locked up.
After the reboot, the call involved does not appear on the call log.
I've Googled this extensively and found many suggestions but no solution that actually works.
I have several questions about what might fix this.
Would an add on dialer app maybe fix this? If so I would be happy to pay for one. Two that I am tire kicking are:
I'd prefer the cheaper one because I don't need all the features of the $10 one. But if the $10 app will fix my problem it will be the best Ten Bucks I ever spent.
I'm also considering the possibility of upgrading to Lollipop. Would that almost certainty fix it? Or might this be a hardware problem?
Lollipop is my second choice for several reasons. It takes me a long time to get my phone just exactly the way I want it. I don't like the aesthetics of the Lollipop UI. I'm concerned that I might never get Flash working on Lollipop. I need flash so I can see weather radar loops. Lots of severe thunderstorms and tornadoes in my area.
Suggestions? New dialer? Lollipop? New phone? Suicide? :-0