Change settlement rule after settlement

[7cows]

I have settled a wbs element in period 4 to a wrong receiver.
I reversed out the settlement.
I tried to change the receiver on the settlement rule and I was not allowed to do so neither could I delete the settlement rule.
I added a new settlement rule with the correct receiver. when I tried to save the wbs element it gave me an error saying the percentage was adding to 200%.

I could not change the To period on the original settlement rule before period 4.

Is there a way I can settle in period to the correct receiver? How do I change the settlement rule receiver?

Thanks in advance