Floating Foilage

So I was setting up a cinematic when out of now where a bunch of foliage that was painted on the landscape correctly is now floating. Only in one large area. Other areas are ok. Any ideas?

Thanks

Luckily, I was able to copy paste the landscape with foilage from another version of the project. Thank God!

I imagine it was due to the engine scalability. Decreasing the landscapes complexity and leaving the foliage where it was.

I could be wrong though.