Doubles and teams divisions have caps. For example, 9b gold is capped at 1650 for three players. 1650 you're in. 1651 you're in platinum. But if you register as a 1650 and move to 1680, you're ok.
I had a buddy who was in gold doubles, 1100 cap. His partner dropped, so he tried to replace him with someone else. Would have been 1100 exactly. Took CSI a week to respond to the request. In that time, the new partner's rating moved up one point. 1101 total now. No go.
Literally one day later he dropped back a few points, back below 1100. New request for the same change. Still no, even though a new registration at that rating would have been fine (and registration was still open.) Got told he had 24hrs to find a partner or his fee would be forfeit. He scrambled, got someone very low, and they ended up going two-and-out.
When I read threads about guys threatening to sue CSI, to parapjrase Chris Rock, "I'm not saying I'd do it. But I understand."