Remove invisible floor of landscape. Lower landscape limit (UE5)

Hello everyone! I’ve been struggling with the issue for couple of months so I would really appreciate your help guys.

The problem is that the player can’t go below some Z point of a landscape.

I am able to make deep sockets and low fields and holes in the landscape and it looks just fine!
But the player won’t go down - they just walk on air and won’t do down any further this invisible floor (((

I want to make an underground cave that goes deep down to the lava itself. Is there a way to do that using the landscape tool?

I’m using UE 5.4.

Example image - ue5 hosted at ImgBB — ImgBB

Thanks!