Hello everyone. Your Android phones have two screen related settings. THE FIRST is called Display. In ''Display', you set things like brightness, font, etc. Here, you also set the Screen timeout (a battery saving feature). Mine is set to 5 minutes.
THE SECOND is ''Lock Screen''. Here, You set your PIN, or password. Lower down (in Lock screen) You get the ''Lock Automatically'' setting. Mine is set to 5 seconds meaning Screen will be locked 5 seconds after Screen automatically turns off. If I make a call longer than 5 minutes my screen will timeout after 5 minutes as I continue that callon that call (whilst the rest of the phone will function as expected.) When I finish the call, my phone will lock straight away - in line with my settings.
There seem to be two ways to resolve the Screen locking after call problem which I've yet to test.
PRECAUTION 1 is to Go to Settings/ Display and to select ''Smart Stay''. This ensures screen stays on as long as you're looking at it and PRECAUTION 2 to set Screen timeout to the max. available value (10 min. On jellybeans 5.0).
PRECAUTION 3 is to exit Display and go in to the Lock Screen settings and set the ''Lock Automatically'' to the max. 30 minutes. What that does, is set your phone to lock 30 minutes after the initial 10 minute time-out. So, I reckon that if your call lasts 15 minutes, it shouldn't lock as described. However, if your call lasts 45 minutes, it'll lock straight after you end the call.
ALSO, the reason your phone's lock after calls is to ensure security as you've set PIN'S & passwords for a reason. That precludes a robber or work colleague getting in to your phone for a nosey after they answer your phone for you ''in good faith''.
Hope this helps.