CineCameraActor PIP View Will Not Update In Real Time For Focal Lengths Under 285.060272 mm

Hi, folks.
I have a CineCameraActor attached to a car pawn, and I wrote a BP allowing me to change the aperture, focus distance and focal length using a gamepad.

In the Editor, when I spawn the CineCameraActor and select it in the Outliner to pop up a PIP view, the view from the camera only updates in real time once the focal length exceeds 285.060272mm (a number derived from very tedious testing). Please see the linked video, which demonstrates the phenomenon, though it was made before I found the extremely precise lower boundary for the focal length. https://youtu.be/M7UD53JL2RE

Between 285.060272mm and 1000mm the PIP updates all changes in real time; view as the camera moves around the level, focus distance, aperture, focal length changes… it all works as expected. As soon as I drop below exactly 285.060272mm the PIP image freezes and no real-time updates are visible.

The virtual lens I’m using is the Universal Zoom, but I tried it with all default focal length prime lenses and none of them with a shorter focal length than 285.060272mm worked.

What could be causing this? Why isn’t the view updating at all focal lengths? Is it an Editor bug? Is it related to HLODs or MIPs?