After update to Unity 5.5 from Unity 5.4 we have noticed this bug: our Vehicles (Rigidbody with BoxCollider) start to pass through the Road Side Walls (Static MeshCollider), this happens only on iOS and only at certain angles between Vehicle and the Wall: On screenshot you can see what I'm talking about: red cube with BoxCollider pass through the MeshCollider. The only workaround is to set different angles for objects with MeshColliders, e.g. we have set of road elements (track constructor) and place them with 0-90-180 degrees to each other, to minimize this bug we have to place this objects like 5-95-175 degrees, etc. Here you can see a short video from iPad: https://dl.dropboxusercontent.com/u/104182758/collision-bug.mov And here the same scene, but with slightly rotated around Y road element, bug doesn't reproduce: https://dl.dropboxusercontent.com/u/104182758/collision-bug-workaround.mov We had sent this bug to Unity: https://issuetracker.unity3d.com/is...ough-each-other-at-certain-angles-on-ios-only Also we would like to warn about this bug because if you use MeshColliders and build games for iOS - you also has it, but it's not easy to catch it. But when it occurs - all in games goes wrong because players could walk where developers don't expect them.