Every time I make it full screen, is jumps back to the primary monitor. This started happening a few days ago, before that it would just work well.
I have to reset in-game options every time to get it to stick to second monitor; but if I remove the full screen once, or close the game and re-open it, it goes back to not letting me full screen on the second monitor.
Have you updated your graphics drivers?
Cos this doesn’t sound like a client issue in my opinion, probably something with your drivers / windows / operating system.
Try holding ALT and pressing the ENTER key, maybe it works, best of luck!
I did update my graphics driver, and nothing to it. ALT+Enter does the same thing, full screen on the second monitor, followed by the screen moving to the first monitor.