U2722D, unwanted switching between sources

I've had the U2722D for a month now and I'm using HDMI and DisplayPort for two different devices. The constant automatic switching between sources is very annoying and it's a problem for me. The U2722D doesn't care what source I have selected, it automatically switches to the active one, even when I manually select the source. I have been using the Dell UltraSharp series for over 10 years and have never had a problem like this. In the previous models I used, I could choose between the sources and Auto. On the U2722D there are the same menu options but they don't work. No matter what I choose, it's always Auto. Is there any solution?