Issue with Landscape

I set up this vr project where O have an open world. I did the whole world with landscape mode and added some layers downloaded from the marketplace. I don’t understand why it appears like two levels were formed and my character walks on one of them resulting in a problem with the overall game. You can see the video. Grass is not foliage but it’s part of the layer (it’s part of the landscape material) so I don’t understand why it acts like that
Here is a video showing the issue, let me know if it doesn’t work. Thank you in advance!