Hi again,
Migrating again to a new project sounds like a good idea. If you do the ‘Migrate’ function on the map/level it will detect assets used in that level and migrate only those. (Helpful for doing a ‘clean’ transfer without unused assets)
In the ‘World Settings’ tab there is a checkbox for ‘Force no precomputed lighting’ - this can be used to clear built lighting.
Swapping lights from Static to Moveable could also change how their shadows look.