Why does my lock screen stop rotating through the images I choose?

[AC Question]

Samsung Galaxy S6 running Nougat. I choose 30 of my favorite pictures for my lock screen to rotate through, and it'll rotate for like a day, and then it just sticks on one picture and I have to go through and pick 30 pictures all over again (I like variety). Why does it keep stopping?? Is it a power/data-saving setting I need to change?

 

[lucianus_luciferus]

I'm guessing it runs through all the pics and once it used all of them it just stays on the last one