It’s almost certainly something engine specific for the 3000ms light problem, but I can’t be sure if there are environmental issues involved as well. Raytracing and Virtual Shadow Maps are likely having some interaction.
Do you get any warnings about VSMs max pages while PIE? If so, use this command to see how many you’re using, and you can adjust the amount inside the DefaultEngine.ini.
r.Shadow.Virtual.MaxPhysicalPages
If that’s not the issue, it’s going to be a tough one to say the least.
For many issues we can talk things a bit through but the nature of a light dropping 3000ms with no discernable reason might just be better to put through a report with some repro steps if you can find them.