Car sink through track

[Kulgera]

Help please!
I do next rbr stage, but have interesting problem, the car just sink through track. At the beginning everything worked, but one moment "vsjoo bizdets"

Video :

 

[martinez]

Too big polygons - make road more dense.

 

[Kulgera]

The solution was defective police-car model, near the falling place. When I delete car model, everything began to work.