f.lux turns off momentarily for apps it is not set to be disabled for.
f.lux has started turning off for a moment (just a second or two or so) when I switch to a program. It gives a notification like "f.lux is disabled for Windows Search / PDF Reader" or the like, and then resumes normal functioning. The only programs I have on my disable list are two games I run in exclusive fullscreen, these other cases are just normal Windows desktop apps.
Windows 10, 64-bit, version 1803 build 17134.228.
f.lux version is 4.76
Graphics card is nVidia GTX 970
Monitor's connected via HDMI.