I think i have managed to find a way to reproduce this but I havent been able to test it a lot as it requires rebooting the tablet.

Have battery graph installed so you can see the cpu usage etc.

1. Reboot the device
2. Make sure that auto lock is turned off
3. Go to the desktop and press the power button
4. Select secure device, do not enter the lock code
5. Put the device in standby
6. Wait for 20 mins
7. Bring the device out of standy and touch outside the lock screen window, it should say device not secured.
8. Open battery graph.

Now you will see that the cpu was been used 100% when the prompt for securing your device was left without any input.

Note. If you enter the code once, the device wont ask you for the code again when you select secure device (unless you reboot), it is the same case if auto lock is enabled.

Someone try this out and confirm so this bug can be reported.