Hi,
Some mesh colliders do not work properly, I had that issue not so long ago, but I admit I was really messing with it, the mesh was very complex, concave, and I was trying to make a collider to conform to that, but I fixed it, by going for convex and change the collision settings like smooth sphere collisions and stuff.
I never had a problem where actually playmaker was not triggering the events where it should, it's always been a case where it was not working in the first place even with a standard script, aka ylways been a prblem with the set up of the collider and gameObject itself.
bye,
Jean