it becomes dark like a photo and a bug appears where all objects look like two

It is being developed using VR, but when the “stereo off”, a normal screen is output.
However, if you “Stereo on”, it becomes dark like a photo and a bug appears where all objects look like two.

In VR, the right eye is not output properly and only the left camera appears.

What are these causes? It appears occasionally and is very difficult to find the cause.

Unreal Engine 5.1