When multiple Watzs are stacked and a meltdown occurs, only the top watz will break leaving the rest of the stack intact. Additionally, the rest of the stack have a maxed out amount of mud but not exploding.

No the problem I am trying to say is that the rest of the segment have a maxed out mud, maybe it should be voided or smt like that.

Mud isn't going to magically disappear, you'll have to drain it before using the reactor again.