Usually when you pay a C/O, it updates to current and you suffer a point loss, unless it was already updating monthly.
Now that it is paid, it can begin to age. Considering it was about to fall off, many would have forgone paying it. When it drops, its irrelevant whether it was paid.
So, he may have seen a drop, unless it was already updating, cuz now it is scored as a fresh late basically.
Its that last one you gotta get off of there. And if its not updating, don't resurrect it, unless you can PFD or something.