mac (book pro) wallpaper issue

Hi, I have a early 2015 macbook pro 13 inch, and I have an annoying problem.

Every time I change my wallpaper, I have to restart my mac, because it won´t change on my homescreen. However, it changes on mission control. When I have 2 external monitors, the second display changes the wallpaper, but the main one doesn´t. I also want to mention that the setting says that the wallpaper is changed. Are there anyone issues, or someone that has experienced it? Help is greately appreciated.

sincerly, Oscar