I've been having an issue of changing the resolution in GNOME Shell in Arch Linux for quite some time now, at least as far back as GNOME 3.12 when I first purchased the display. With my Seiki monitor, I'm essentially stuck at using 3840x2160 and am unable to change the resolution to 1920x1080 at all unless I manually modify the ~/.config/monitors.xml file. Essentially what happens if that if I am using Arch Linux, and attempt to change the display, the screen turns black and then reappears at the same resolution. If I attempted the change through GNOME Displays, it will ask if I want to keep the new resolution, even though it's the same resolution as before.

Attempting to change the resolution either through GNOME Display or xrandr causes the DRM to hotplug twice within a second and simply revert back 3840x2160, and so a GNOME developer told me that the problem is in the kernel because the DRM is not supposed to do that at all. It affects both GNOME and Wayland sessions, so it's not a bug with Xorg either. I am, however, able to change the resolution when using a different desktop environment, like i3-wm, so I'm not entirely sure if it's a bug with the kernel or mutter itself on both Wayland and Xorg sessions.

I've just installed Gentoo recently alongside Arch Linux with GNOME 3.16 and have noticed that the problem is not present there at all. I can change the resolution from 3840x2160 to 1920x1080 and back as many times as I want and there isn't a single issue, which leads me to believe that there is a packaging bug in Arch Linux, perhaps in how the kernel is being built. This happens on all three of my Arch Linux systems, and all of which are using RadeonSI hardware running the open source drivers, and I do not own anything with Intel or NVIDIA graphics. I will note, however, that I have no problems changing the resolution when using other non-4K 1080p displays, so this is very much an issue with 4K monitors.