Why is my lock screen delaying opening?

Hi guys..
For few days I have a problem with my Lumia 1320. When I press the button to unlock my phone on the screen I can see the message Resuming... And is like that about 5-6 seconds and after that unlocks the phone and that start annoying me. It wasn't like that before a week. I reset my phone few times, but nothing so far.
Any ideas?

Go to settings > lock screen > choose Bing > choose photo

Do you use live lock screen beta by chance?

i had this issue with tetra lockscreen

If you're using Live Lockscreen Beta or Tetra Lockscreen, please see this article and use Kids Corner to get rid of the resuming bug.