Had to try. I also am using FPP, not xLights output, so I had never tried it.
My xlights setup is a very simple 128 universes (512, not 510) of all multicast.
Clicking output to lights did not crash v4.2.13.
Bonus: I did get lights received on my F16V2 on the appropriate universe (starting at 33)
What is your xLights channel setup?