I've just started using Elementary OS, and I'm having a bit of trouble with the resolution saving. My monitor/tv's native resolution is 4K, but I prefer to run in 1080p. When the login screen boots up, it's always in 4K, then when I login, I have to change to 1080p, it never saves. The other thing is that when I change the resolution to 1080p, the mouse cursor is huge because it is the 4K mouse cursor. Could anyone give me a bit of help? Other than that I'm pretty happy with the operating system as a whole. Few bits here and there but overall okay.
what graphics card do you have, which version of ElementaryOS are you running
You can use the following command in the terminal to decide which graphics card you have
sudo lspci|grep VGA
To me it seems like a driver issue so the answer about it depends on the card and driver you are using.