I have greetd set up to use sway and wlgreet as a greeter, and sway is configured to turn the displays off via DPMS after some inactivity. Often times when the displays turn back on, wlgreet isn't visible on the screen. I still see a wlgreet process running, but I can't see the login prompt.
This only happens when multiple displays are connected, and outputMode = "active" in wlgreet.toml. If outputMode = "all", the prompt is still visible on all displays, but slightly off-center by about 5% both down and right.
Also, I see this behavior on machines that uses AMD graphics, but I don't see this behavior on machines that uses Nvidia or Intel graphics.