I recently bought an A50 (and promptly broke it, but the handset was repaired and was working perfectly well until this issue arose). It now has a fairly perplexing display/screen error.
When the screen turns off, the phone then ceases to respond to anything that would make the screen turn back on. Tapping the screen or pressing the power key has no effect, though the phone remains clearly on - it vibrates for notifications and alarms, and can even receive calls, though the screen never turns on after the first time it deactivates.
Performing a soft reboot of the device means the screen will turn back on and will function normally, but only until the screen turns off again, which also occurs randomly, sometimes only seconds after the phone is turned back on. It usually requires several consecutive soft reboots before the screen will allow itself to remain on indefinitely. There is no consistent cause for the screen turning off, as it seems to happen regardless of what is happening in the foreground. The only thing that has been able to consistently cause the bug is when entering the PIN when trying to change the lock type, which causes an immediate screen turnoff.
When the phone is charging, the screen will respond normally. The screen will sometimes randomly turn off, but it will then turn back on as it normally should with either the screen-tap or through the power key. As soon as the phone is disconnected from the charger, the problem then resumes.
The problem persists at full battery and low battery; with its case and without its case; in safe mode and in normal mode; after a full factory reset; with no apps open; and with a cleared cache.
I'd take it in to the shop I bought it from but after the last repair they lost the records of having sold it to me so I wouldn't be able to use their fastest repair, and I need the handset (temperamental as it may be when not charging, and sometimes while it is) for work and cannot afford to be without it for the fortnight the normal repair speed takes.
I'm happy to answer any further questions and I hope someone else has either experienced and solved this issue, or recognises the root cause. Thank you for reading.
Have you checked to see if there are any software updates available for your phone? Go to Apps > Settings > Software update > Download and install. If this doesn't help, it sounds as though one of our engineers will need to take a look at the phone. Are you anywhere near one of our Service Centres?: http://www.samsung.com/uk/support/servicelocation/