Have you tried restarting the tablet? Also make sure the screen has nothing impeding it. Scratches, smudges, etc.
Should it not be that, then I would try starting it up in "Safe Mode" and see if the problem happens in there. If not, then you have something on the device that is causing the issue. Bad app, resource hogging app, virus, malware, etc. You would have to remove what is causing the problem to get it to work correctly.
Now if this only happens when using a specific app, or after having used a specific app, then I would look at the app as the problem.
To get into "Safe Mode" please do the following.
1. First turn off the tablet.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.