For some time, I had in my scene some capsule shapes, boxes and a heightfield. All of them working correctly.
However, lately I added a btBvhTriangleMeshShape created using btTriangleIndexVertexArray which collides with btCapsuleShape and btBoxShape shapes. But it simply goes through the btHeightfieldTerrainShape.
It is not going at an abnormal velocity, but either way I tried some Anti tunneling by Motion Clamping without any result.
The physical debug renderer shows all the objects including the new btBvhTriangleMeshShape, so I presume that the trimesh was created correctly. Below is a screenshot with a Barrel loaded as a btBvhTriangleMeshShape: