No light after the project loads

Hello,
After loading a project created in V3.1,
the light is missing.

If I select a different scene, everything works fine in that one.
But when I go back to the first scene, the light is on there, too.
Most of the time, anyway—not always.

This is some weird behavior from V3.1.

I have a PC with an RTX 5090 and 64 GB of RAM; the current graphics driver is 610.74.

Bye
Andreas