Every once in a while calc gets loaded in the background on my second screen. This happens about 4 times a day and no I do not have a multimedia keyboard that could have a stuck key, but I heared from other places this might be an issue in Displayfusion. The only other program that interacts with Displayfusion I know of that I have is Classic Shell.

Calc seems to be opened/showed in a suspended state according to Windows 10 task manager.