Why does my "call ended" screen get stuck as an open task?

[AC Question]

I own a LG G2 with Lollipop and it's just a few weeks old. No root, no strange apps installed. Well configured.

Sometimes, after I end a call and go to the open tasks list (square symbol), there's a task whose image is the "call ended" screen that appears right after I (or the other person) hang up.

Besides that, which is strange enough by itself, when I close this task and open the tasks list again, there it is: the same task! If I call someone else and hang up, the task changes its image to the "call ended" screen with that last person's number.

I'm really lost here. Any help would be appreciated!
Thanks in advance!

 

[B. Diddy]

Welcome to Android Central! The Recent Apps list isn't a task manager--so apps that you see aren't necessarily "open tasks." It's simply a list of your recently used apps. It's true that some of these apps may still be paused in the background, and swiping them away will close them out completely--but not for all of them.