Speculation welcome - I have at least two ideas but they're probably both wrong.
Noticed a couple of things I think might be related so far:
- The discoloration on the back inside of the cups
- The half circle you can just barely see on the right inside of the cups
- The under table mechanism seems related to the ball movement but there isn't quite enough of a sample for me to work out how.
- Is it the same ball? I'm not positive.