We can't say anything based solely on the scale of the terrain. The issue is the interaction of movement, usually small values, and position.
The original problem was falling through the terrain. Where does this happen? If it is very far from (0,0,0) then you should suspect floating point accuracy as the reason.
Similarly, there are issues with very steep terrain. Again, this is most likely a result of mixing large and small numbers. On steep terrain a small horizontal movement induces a large vertical movement.
The original problem was falling through the terrain. Where does this happen? If it is very far from (0,0,0) then you should suspect floating point accuracy as the reason.
Similarly, there are issues with very steep terrain. Again, this is most likely a result of mixing large and small numbers. On steep terrain a small horizontal movement induces a large vertical movement.