scene.onPointerDown and ActionManager do not work well with each other.
When an ActionManager is added to a mesh, the mesh becomes unpickable by the onPointerDown function
see playground example
http://www.babylonjs-playground.com/#1UTZEV#13
with lines 42 to 53 commented out everything works fine. The sphere is pickable.
Click the sphere and check the console message. It shows it was picked
un-comment only line 42.The sphere is no longer pickable.
un-comment line 42 to 47. sphere becomes pickable.
un-comment line 42 to 53. sphere becomes unpickable.
Please check.