Car "bugs" through ground

Hello!

I have 2D game where you play football with cars, but i have problem - car can "bug" into ground when it has enough speed :/ and sometimes it "bug" even with small speed but in specific position. Car and ground have polygon colliders and it bugs not just with ground but also with net and walls... :/

It's unity2d bug or i have to set some setting?

Video is here:

https://www.youtube.com/watch?v=AlPTC30YLJI

And screenshots here:

alt text

Please help... :)