Create a new Class Blueprint
with both windows open, the main UE4 level editor and class blueprint side by side.
Drag a lights\spotlight from the main UE4 editor to your class blueprint components window.
Instead of having a spotlight, a regular point light will be created instead.
Easy work around is add the spotlight component from the BP window.
The reason that this doesn’t work is because you’re trying to move a Spot Light actor into the blueprint when you drag it from the main editor. Adding the spot light in the blueprint itself adds a spot light component, which is why it works as intended when you add it that way. Hope that helps.