U3818DW, Contrast, Gamma or Brightness changing sporadically

Hi,

I am new to my U3818DW, Service Tag: and  Serial Number: CN-097F8P-QDC00-7BR-06DL. But have noticed that the display's contrast or brightness or gamma changes sporadically as I use the computer. I have the Dell Display Manager installed and have everything set to "standard" so I don't think any specific application is telling the display to change its character. Also, because I am using EVGA graphics adapters, NVIDIA control panel has NVIDIA controlling the color, etc., and not a specific application. Are there any recommendations as to where else to look?