We're three handed. I've got $50,000, Claptrap has 30,000, and Sam has 10,000.
I raise to $4000 preflop.
Claptrap re-raises to $9000. (5000 on top)
Sam shoves for $10,000. (1000 on top)
Claptrap shoves for $30,000...
That's an illegal move. Sam's raise was less than 1/2 the size of the previous raise. (This is only allowed if you go all-in.) A call of a raise of less than 1/2 the size of the previous raise is not considered a "legal" raise, and only a "legal raise" can re-open the betting. Claptrap's options in that spot are to either call $1000 or fold.
And yes, I have video of this in case you want to reproduce it.