Display Tablet Turning Off

[AC Question]

Good Morning all, I hope that you are well.

My company have recently purchased a meeting room booking system, and included in this system are Android tablets(ASUS tf103c) placed outside the meeting rooms, displaying specific information.

The tablets are powered by plugging into the mains and the tablets show as AC when charging, the tablets keep turning off after a day or so, or sometimes they last more than a day.

Things I've tried so far:
1. Installed Llama to power the displays off at night so it doesn't draw battery
2. Lowered the brightness to half to prolong battery and screen life.
3. Uninstalled and stopped any irrelevant applications.
4. Installed 'Keep Alive' app that forces the tablets screen to stay on.
5. Enabled Developer mode and ticked 'stay awake'

The problem that I have here is that the tablets are not going to sleep, they are completely draining and turning off, then fully charging when powering back on, this means we have to go around and power them up every morning, not very time friendly for our busy IT team.

Android Version 4.4.2

Any help would be greatly appreciated, I'm really struggling here.

Thanks,

Hassan.