Hello Dado,
Check your normals. That is where you problem lies

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In the photo above, in "wood" texture, is my collision mesh (a plane, so no thickness) with normals indicated by the green arrow.
When the car is attacking from A side, never experienced any problems;
When the car is attacking from B side, sometimes (if small speed essentially) no problem; but more often the car will partially pass through the wall, or remain hanged.
So I would say first thing to check is normals.