[4.9] Weird shadows after light compiling

Hello everyone, I’ve a problem that I can’t solve without your help. I’ve this situation:

This preview:

with pretty good lights (but uncompiled), and THIS fter compiling:

All the assets are from SunTemple from Epic Games.
What I’ve to do for fix this weird problem?

Thank you in advance!

PROBLEM SOLVED:

The problem was in the floor’s UV. I’ve used a stretched mesh. Stretching them esh I’ve also stretch the UV. I’ve solved replacind the mesh with a BSP. After the replace I’ve converted it in a mesh with the right UV and the shadows are now fixed!