Collission test not returning all contacts

[xerion]

Hey all,

I am doing some frustrum culling and then narrowphase collision detection but it seems that in some cases not all the collisions are returned.
For example I have a plane object represented in bullet as a convex shape of 4 points (the issue I am seeing is mainly related to convex shapes and not with box, sphere, etc..).

You can see in the attached screenshot, the plane along with the bullet object ( debugDrawWorld() ).
The other object is a btPairCachingGhostObject and its shape is the convex of the frustrum (8 points) that is constructed on mouse click.
It clearly has a contact with the plane convex shape but in this case there are no contacts returned.

Depending where I click I either get a contact result or not.

Any ideas of what's possibly going on ?