Windows has horrible DPI handling.
The worst thing is lack of multiple (per display DPI handling).
I have here a 1080p display and 4k display that shows those strange behaviors. FLStudio on the 1080 shows fine but on the 4k it decides actually to become smaller with higher DPI.
Let’s hope Windows 10 RS3 will understand people need DPI to be per display. (macOS can have HiDPI and 1:1 resolutions pretty well).