Line Drawing Issue in 3D Environment

I was getting a line issue when my car moves on the track. Here you have a screenshot for this:

This kind of line is not always displaying but when the car was moving, sometimes it shows this kind of line. Actually, this is a hole that gets generated later in the gameplay.

See below image for a more clear idea:

I have properly checked that the block that will generate a hole that is placed properly. But this is not an issue and because of this reason, it was not displaying always but when my car reaches this place.
Give me some solution for this line hiding.