phone works until locking screen

Hi All,

Weird problem, I was given a phone to look at (Samsung A20e), and it all works until the phone goes into sleep mode (unused) or when the power button is pressed, the phone still works in background as it will still "beep" when receiving emails and stuff, but when you try and unlock the screen nothing is shown, the power button doesn't appear to do anything, however, when you use the power button and the down vol button to force reboot, then this does work and the phone reboots and you can use it again until the screen locks.
Furthermore when the screen is active the power button when pressed does show 3 options, power off, restart and emergency call. So the power button does work, but the power button doesn't seem to be recognised after the screen is locked. Not sure if anyone has come across this before, I have seen others mention, but I can't see a solution for this issue.

I have done the usual :
- factory reset
- Safe mode
- rebooted
- stripped and cleaned ribbon connectors

Any ideas would be appreciated.

Cheers