Sometimes they hold the arrears for a while and then give it to you at one time
When DH paid his ex wife for CS arrears it took like 6 months for her to receive it
Quoting Yurvette [♥]:" Any reason WHY they do that? That is stupid... "
In my experience, they paid everything straight to me - however, I have been under the impression that sometimes, if more than what is due is paid in a month, they will hold some back and pay you later.
However, since you're not actually getting the cash, I don't get why the arrears would affect anything...