macOS El Captain.
Cocoa app. I dont have a demo but I can see it in CudaText:
in CudaText I enter console line which makes dialog with Memo+Button.
Memo coords: 10,10-100,30
Button coords: 110,10-200,30
but Button is painted 3-5 pixels lower than memo.
I also see this effect in CudaText dialogs: some buttons painted lower.