Problems with Physics (bouncing balls)

• If I put a ball at the start of a scene, it drops and bounces properly. That tells me the physics and gravity settings are fine.
• If I make the puppet appear after the start of a scene (trim the left edge of the puppet bar in the scene window), the ball appears at the right time, but it does not drop - it stays stuck at its original position.
  
  
  
• If I add a trigger to the puppet and make the physics as "start when triggered", triggering the puppet makes it appear but it just sits there again, not falling
• If I arm/disarm the ball puppet in the scene in edit mode, it starts dropping

Am I doing something wrong here?  Feels like the "reset ball" or "start physics moving" is not quite right.

I worked around it - I split the scene in two so the ball starts dropping at the start of the second scene (all is good then) - but was wondering if there is something obvious I am missing.