Vive Pro Mirror output is scaled in packaged build

Since switching to 4.23 I have been having trouble with the monitor screen in my VR project when using the Vive Pro.
What happens is that the monitor screen only displays roughly the top left quarter of the view. I have found a workaround in the editor, by setting ‘Enable HMD’ to true and then to false again. However, this does not work in a packaged build.

Some notes:

  • I made a test project using the VR Template in UE4 with just a simple widget as a menu.
  • It also affects the UI (menu is also scaled), when Enable HMD is false, the menu is sized correctly visually, but the hit detection for buttons was still as if it was scaled. It was also as if ScreenPercentage was at 200 (which I made sure it wasn’t).
  • I tried the exact same node setup in 4.21 and it worked correctly.
  • I tried the exact same node setup with an Oculus Rift CV1 attached and it worked correctly.

I would like to know if anyone else is having the same problem and if anyone knows why this is happening and how to fix it.

Hopefully the following images make the problem a bit clearer.
Also note the hover state (red) and the positioning of the mouse.

Node setup in the Level Blueprint:

This is what the test menu should look like (and does in the editor after enabling en disabling HMD):

This is the visually correct menu with incorrect hit detection:

This is the scaled (hit detection is correct) version of the menu in a build. Using the same node setup:

The view of the camera in a build. The red dot shows roughly the center of the view: