[RESOLVED] Collisions sometimes not occuring in Unity 2018.2

Hi,

I am looking into upgrading my project from Unity 2017.4 LTS to 2018.2. I cannot upgrade to 2018.3 or higher because the changes to PhysX break parts of my game significantly (I can explain this in further detail if requested, but it's not related to this problem).

Most things with the physics in 2018.2 seems to be fine, however I am having an issue where some of my objects are not colliding at all. For example in this screenshot:

If apply force to the ball, it will collide with the floor, the walls and the red plane, but it will not collide with the yellow block and blue pinball bumper thing. Also, raycasts will not hit these objects.

All objects are instantiated at runtime. The floor and the wall meshes are generated at runtime whereas everything else is a prefab.

If I drag the same prefab into the scene while playing, collisions work correctly on that object. If I change any property on the collider it will start working. I've played with the mesh cooking options and physics settings and nothing seems to have any affect. I also checked the layers and everything is fine there (the walls and the block and pinball bumper are on the same layer).

Thanks for any help.

 

Gah, as per usual I discover the solution shortly after I post something about it.

I didn't think to check the exact version of 2018.2 I was running, turns out I was on 2018.2.0. Updating to 2018.2.21 fixes my problem.