If you are using the Fence Generator and suddenly find yourself with a lighting error like this that refuses to go away no matter how many time you rebuild you level:
“MapCheck:Error: Error MyWorldSettings Maps need lighting rebuilt”,
then you need to take a look at your generated fences. I spent several hours trying to figure out why I couldn’t build the lighting successfully. Hacking the editor finally revealed the source of the problem which was several problematic fence segments created by the fence generator. I didn’t dive into the blueprint, but it seems that there are splines being created that are causing problems for the lighting build. I don’t know if this is a problem with the engine splines or an issue with the blueprint itself misusing the splines. But I do know it’s hard to trace if you have a lot of fencing.