I come with a very very late reply, but since i got this issue and i still dont see any answer that actually fixs it i decided to write what worked for me.
I tried using the “Foliage” LOD Group as many said here, but since im using my own LODs made by me, i had to import them again and change all the settings again… which adds extra work and it still did not fix my problem.
What did fix it though is to simply change the lighting of the mesh im using as foliage from “static” to “movable”.
So Foliage → Select the mesh → Instance Settings → Mobility change to “Movable” instead of “Static”
About how much this affects performance i dont know, but it finally deleted the messege when building lighting.
Hope it helps someone in the future.
