Nvidia DSR Resolution Issue

A player of mine has Nvidia 4x DSR set up in their control panel, so despite having a 1920x1080 monitor, they can use a downscaled 3840x2160 resolution.

The problem is that selecting the DSR resolution in the game doesn’t do anything. With Fullscreen selected, selecting the above resolution and accepting the change results in no actual change in resolution.

If in Windowed mode, the resolution changes, but the UI and game itself doesn’t appear to stretch to fit the new resolution, and instead squishes itself into the top-left quarter of the screen. If they then switch back to Fullscreen, the desired resolution is correctly applied.

However, quitting and re-entering the game results in it reverting back to 1920x1080 resolution (even though 3840x2160 is still selected in the auto-populated dropdown menu).

Is this a general issue with the Unreal Engine, or is there a specific Window Mode I can enable to prevent these problems?