Sleep timer under Display settings won't stay where I set it.

Settings/Display/Sleep. It's always set on 1 minute, whether I change it or not. I've tried setting it to 5 mins and it goes right back to 1 min. None of my changes will stay. Always 1 min. My tab is not rooted and its up to date.
I cannot find the answer anywhere. Any searches I make on Sleep never give me the correct search. I am at my wits end. It's extremely annoying when reading something and the display closes down. I always have to press the Power button to wake it up.
Please give me some suggestions.
Thanks:(:(