Nice rattles Jim. I usually use shellac burn in sticks for my fills, and on stuff that lies around, or even gets stuff piled up on it, I've never had issue with  it coming out, BUT then again I have never put metal balls inside something, and given it to a toddler either. If something can get destroyed, a small child can get the job done. Maybe just let Mom know there is a fill material, and if she gets any leakage, send it back to you for repair?

That BE is wormy, I wonder if it was on the ground a while before it got processed?

Did you get a result on the site problem? I've looked at it a few times, and I can't figure it out?